Maiman, T. H. Stimulated optical radiation in ruby.Nature187, 493-494 (1960)..

Glauber, R. J. The quantum theory of optical coherence.Phys. Rev.130, 2529-2539 (1963)..

Ready, J. F.Industrial Applications of Lasers. 2nd edn (Academic Press, London, 1997).

Schubert, M. et al. Lasing within live cells containing intracellular optical microresonators for barcode-type cell tagging and tracking.Nano Lett.15, 5647-5652 (2015)..

Schubert, M. et al. Monitoring contractility in cardiac tissue with cellular resolution using biointegrated microlasers.Nat. Photonics14, 452-458 (2020)..

Wang, Z. H. et al. Bio-electrostatic sensitive droplet lasers for molecular detection.Nanoscale Adv.2, 2713-2719 (2020)..

He, L. N. et al. Detecting single viruses and nanoparticles using whispering gallery microlasers.Nat. Nanotechnol.6, 428-432 (2011)..

Humar, M.&Hyun Yun, S. Intracellular microlasers.Nat. Photonics9, 572-576 (2015)..

Wu, X. Q. et al. Nanowire lasers as intracellular probes.Nanoscale10, 9729-9735 (2018)..

Chen, Y. C., Chen, Q. S.&Fan, X. D. Lasing in blood.Optica3, 809-815 (2016)..

Sun, Y. Z. et al. Bioinspired optofluidic FRET lasers via DNA scaffolds.Proc. Natl Acad. Sci. USA107, 16039-16042 (2010)..

Xavier, J. et al. Advances in optoplasmonic sensors—combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles.Nanophotonics7, 1-38 (2018)..

Taylor, A. B.&Zijlstra, P. Single-molecule plasmon sensing: current status and future prospects.ACS Sens.2, 1103-1122 (2017)..

Liang, F. et al. Photonic-plasmonic hybrid single-molecule nanosensor measures the effect of fluorescent labels on DNA-protein dynamics.Sci. Adv.3, e1602991 (2017)..

Levene, M. J. et al. Zero-mode waveguides for single-molecule analysis at high concentrations.Science299, 682-686 (2003)..

Yu, W. Y. et al. Cavity optomechanical spring sensing of single molecules.Nat. Commun.7, 12311 (2016)..

Mauranyapin, N. P. et al. Evanescent single-molecule biosensing with quantum-limited precision.Nat. Photonics11, 477-481 (2017)..

Duff, D. G., Baiker, A.&Edwards, P. P. A new hydrosol of gold clusters. 1. Formation and particle size variation.Langmuir9, 2301-2309 (1993)..

Vincent, S., Subramanian, S.&Vollmer, F. Optoplasmonic characterisation of reversible disulfide interactions at single thiol sites in the attomolar regime.Nat. Commun.11, 2043 (2020)..

Vollmer, F., Arnold, S.&Keng, D. Single virus detection from the reactive shift of a whispering-gallery mode.Proc. Natl Acad. Sci. USA105, 20701-20704 (2008)..

Trichet, A. A. P. et al. Nanoparticle trapping and characterization using open microcavities.Nano Lett.16, 6172-6177 (2016)..

Venkatakrishnarao, D. et al. Advanced organic and polymer whispering-gallery-mode microresonators for enhanced nonlinear optical light.Adv. Optical Mater.6, 1800343 (2018)..

Rayleigh, L. C. X. I. I. The problem of the whispering gallery.Lond., Edinb., Dublin Philos. Mag. J. Sci.20, 1001-1004 (1910)..

Foreman, M. R., Swaim, J. D.&Vollmer, F. Whispering gallery mode sensors.Adv. Opt. Photonics7, 168-240 (2015)..

Tavernier, H. et al. Magnesium fluoride whispering gallery mode disk-resonators for microwave photonics applications.IEEE Photonics Technol. Lett.22, 1629-1631 (2010)..

Jiang, X. F.&Yang, L. Optothermal dynamics in whispering-gallery microresonators.Light. Sci. Appl.9, 24 (2020)..

Grundmann, M.&Dietrich, C. P. Whispering gallery modes in deformed hexagonal resonators.Phys. Status Solidi (B)249, 871-879 (2012)..

Garrett, C. G. B., Kaiser, W.&Bond, W. L. Stimulated emission into optical whispering modes of spheres.Phys. Rev.124, 1807-1809 (1961)..

Benner, R. E. et al. Observation of structure resonances in the fluorescence spectra from microspheres.Phys. Rev. Lett.44, 475-478 (1980)..

Li, G. H. et al. Record-low-threshold lasers based on atomically smooth triangular nanoplatelet perovskite.Adv. Funct. Mater.29, 1805553 (2019)..

Wang, D. et al. Lasing in whispering gallery mode in ZnO nanonails.J. Appl. Phys.99, 093112 (2006)..

König, K. Multiphoton microscopy in life sciences.J. Microsc.200, 83-104 (2000)..

Sandoghdar, V. et al. Very low threshold whispering-gallery-mode microsphere laser.Phys. Rev. A54, R1777-R1780 (1996)..

Yan, D. D. et al. Stable and low-threshold whispering-gallery-mode lasing from modified CsPbBr3 perovskite quantum dots@SiO2 sphere.Chem. Eng. J.401, 126066 (2020)..

Wu, Y. Q., Ward, J. M.&Nic Chormaic, S. Ultralow threshold green lasing and optical bistability in ZBNA (ZrF4-BaF2-NaF-AlF3) microspheres.J. Appl. Phys.107, 033103 (2010)..

Herr, S. J., Buse, K.&Breunig, I. LED-pumped whispering-gallery laser.Photonics Res.5, B34-B38 (2017)..

Ilchenko, V. S.&Matsko, A. B. Optical resonators with whispering-gallery modes-part Ⅱ: applications.IEEE J. Sel. Top. Quantum Electron.12, 15-32 (2006)..

Zhang, S. X. et al. Free-space coupling efficiency in a high-Qdeformed optical microcavity.Opt. Lett.41, 4437-4440 (2016)..

Kuehne, A. J. C.&Gather, M. C. Organic lasers: recent developments on materials, device geometries, and fabrication techniques.Chem. Rev.116, 12823-12864 (2016)..

He, L. N., Özdemir, S. K.&Yang, L. Whispering gallery microcavity lasers.Laser Photonics Rev.7, 60-82 (2013)..

Lu, T. et al. A narrow-linewidth on-chip toroid raman laser.IEEE J. Quant. Electron.47, 320-326 (2011)..

Jun, Y.&Guo, L. J. Optical sensors based on active microcavities.IEEE J. Sel. Top. Quantum Electron.12, 143-147 (2006)..

Himmelhaus, M.&Francois, A. In-vitro sensing of biomechanical forces in live cells by a whispering gallery mode biosensor.Biosens. Bioelectron.25, 418-427 (2009)..

Weiss, D. S. et al.Splitting of high-Q Mie modes induced by light backscattering in silica microspheres.Opt. Lett.20, 1835-1837 (1995)..

Chen, W. J. et al. Parity-time-symmetric whispering-gallery mode nanoparticle sensor[Invited].Photonics Res.6, A23-A30 (2018)..

Özdemir, S. K. et al. Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser.Proc. Natl Acad. Sci. USA111, E3836-E3844 (2014)..

Yuan, Z. Y. et al. Lasing-encoded microsensor driven by interfacial cavity resonance energy transfer.Adv. Optical Mater.8, 1901596 (2020)..

Shopova, S. I. et al. Optofluidic ring resonator based dye laser.Appl. Phys. Lett.90, 221101 (2007)..

Lee, W. et al. Digital DNA detection based on a compact optofluidic laser with ultra-low sample consumption.Lab Chip16, 4770-4776 (2016)..

Gong, C. Y. et al. Distributed fibre optofluidic laser for chip-scale arrayed biochemical sensing.Lab Chip18, 2741-2748 (2018)..

Feng, Z. Q.&Bai, L. Advances of optofluidic microcavities for microlasers and biosensors.Micromachines9, 122 (2018)..

Bog, U. et al. On-chip microlasers for biomolecular detectionviahighly localized deposition of a multifunctional phospholipid ink.Lab Chip13, 2701-2707 (2013)..

Li, X. Z. et al. Ultrasound modulated droplet lasers.ACS Photonics6, 531-537 (2019)..

Duan, R. et al. Detection of acetylcholinesterase and its inhibitors by liquid crystal biosensor based on whispering gallery mode.Sens. Actuators B: Chem.308, 127672 (2020)..

Ouyang, X. et al. Ultrasensitive optofluidic enzyme-linked immunosorbent assay by on-chip integrated polymer whispering-gallery-mode microlaser sensors.Lab Chip20, 2438-2446 (2020)..

Chen, Y. C.&Fan, X. D. Biological lasers for biomedical applications.Adv. Optical Mater.7, 1900377 (2019)..

Tan, X. T. et al. Fast and reproducible ELISA laser platform for ultrasensitive protein quantification.ACS Sens.5, 110-117 (2020)..

van Nguyen, T. et al. Egg white based biological microlasers.J. Phys. D: Appl. Phys.53, 445104 (2020)..

Mai, H. H. et al. Chicken albumen-based whispering gallery mode microlasers.Soft Matter16, 9069-9073 (2020)..

Maayani, S., Martin, L. L.&Carmon, T. Water-walled microfluidics for high-optical finesse cavities.Nat. Commun.7, 10435 (2016)..

Avino, S. et al. Direct sensing in liquids using whispering-gallery-mode droplet resonators.Adv. Optical Mater.2, 1155-1159 (2014)..

Giorgini, A. et al. Liquid droplet microresonators.Sensors19, 473 (2019)..

Humar, M.&Yun, S. H. Whispering-gallery-mode emission from biological luminescent protein microcavity assemblies.Optica4, 222-228 (2017)..

Yang, S. C. et al. Reconfigurable liquid whispering gallery mode microlasers.Sci. Rep.6, 27200 (2016)..

Ta, V. D., Chen, R.&Sun, H. D. Tuning whispering gallery mode lasing from self-assembled polymer droplets.Sci. Rep.3, 1362 (2013)..

Wang, Y. et al. Robust whispering-gallery-mode microbubble lasers from colloidal quantum dots.Nano Lett.17, 2640-2646 (2017)..

Aas, M. et al. Spectral tuning of lasing emission from optofluidic droplet microlasers using optical stretching.Opt. Express21, 21380-21394 (2013)..

Jonáš, A. et al. In vitro and in vivo biolasing of fluorescent proteins suspended in liquid microdroplet cavities.Lab Chip14, 3093-3100 (2014)..

Aas, M., Jonáš, A.&Kiraz, A. Lasing in optically manipulated, dye-doped emulsion microdroplets.Opt. Commun.290, 183-187 (2013)..

Alford, R. et al. Toxicity of organic fluorophores used in molecular imaging: literature review.Mol. Imaging8, 341-354 (2009)..

Chen, L. J. et al. Microfluidic fabrication of cholesteric liquid crystal core-shell structures toward magnetically transportable microlasers.Lab Chip16, 1206-1213 (2016)..

Anand, S. et al. Observation of whispering gallery modes in elastic light scattering from microdroplets optically trapped in a microfluidic channel.J. Optical Soc. Am. B33, 1349-1354 (2016)..

Karadag, Y. et al. Dye lasing in optically manipulated liquid aerosols.Proceedings of the SPIE 8810, Optical Trapping and Optical Micromanipulation X(SPIE, San Diego, 2013).

Azzouz, H. et al. Levitated droplet dye laser.Opt. Express14, 4374-4379 (2006)..

Tona, M.&Kimura, M. Novel lasing modes observed in a levitated single dye-doped microdroplet.J. Phys. Soc. Jpn.69, 3533-3535 (2000)..

Humar, M. et al. Biomaterial microlasers implantable in the cornea, skin, and blood.Optica4, 1080-1085 (2017)..

Wei, C. et al. Organic Janus microspheres: a general approach to all-color dual-wavelength microlasers.J. Am. Chem. Soc.141, 5116-5120 (2019)..

van Nguyen, T. et al. Protein-based microsphere biolasers fabricated by dehydration.Soft Matter15, 9721-9726 (2019)..

Wei, Y. H. et al. Starch-based biological microlasers.ACS Nano11, 597-602 (2017)..

Resch-Genger, U. et al. Quantum dots versus organic dyes as fluorescent labels.Nat. Methods5, 763-775 (2008)..

Mérian, J. et al. Fluorescent nanoprobes dedicated to in vivo imaging: from preclinical validations to clinical translation.Molecules17, 5564-5591 (2012)..

Zheng, L. et al. Embedding liquid lasers within or around aqueous microfluidic droplets.Lab Chip18, 197-205 (2018)..

Kiraz, A., Chen, Q. S.&Fan, X. D. Optofluidic lasers with aqueous quantum dots.ACS Photonics2, 707-713 (2015)..

Gardner, K. et al. Ultrabright fluorescent and lasing microspheres from a conjugated polymer.Adv. Funct. Mater.28, 1802759 (2018)..

Tang, S. J. et al. A tunable optofluidic microlaser in a photostable conjugatedpolymer.Adv. Mater.30, 1804556 (2018)..

Nizamoglu, S., Gather, M. C.&Yun, S. H. All-biomaterial laser using vitamin and biopolymers.Adv. Mater.25, 5943-5947 (2013)..

Chen, Q. et al. Optofluidic lasers with a single molecular layer of gain.Lab Chip14, 4590-4595 (2014)..

Wu, X. et al. Bio-inspired optofluidic lasers with luciferin.Appl. Phys. Lett.102, 203706 (2013)..

Chen, Y. C., Chen, Q. S.&Fan, X. D. Optofluidic chlorophyll lasers.Lab Chip16, 2228-2235 (2016)..

Anashkina, E. A. Laser sources based on rare-earth ion doped tellurite glass fibers and microspheres.Fibers8, 30 (2020)..

Yang, L. et al. Erbium-doped and Raman microlasers on a silicon chip fabricated by the sol-gel process.Appl. Phys. Lett.86, 091114 (2005)..

Mondal, S. et al. Investigation of optical and electrical properties of erbium-doped TiO2thin films for photodetector applications.J. Mater. Sci. Mater. Electron.29, 19588-19600 (2018)..

Ward, J. M., Yang, Y.&Nic Chormaic, S. Glass-on-glass fabrication of bottle-shaped tunable microlasers and their applications.Sci. Rep.6, 25152 (2016)..

Lei, F. C. et al. Pump induced lasing suppression in Yb: Er-doped microlasers.Opt. Express25, 24679-24689 (2017)..

Reynolds, T. et al. Fluorescent and lasing whispering gallery mode microresonators for sensing applications.Laser Photonics Rev.11, 1600265 (2017)..

Fernandez-Bravo, A. et al. Continuous-wave upconverting nanoparticle microlasers.Nat. Nanotechnol.13, 572-577 (2018)..

Ruan, Y. L. et al. Tellurite microspheres for nanoparticle sensing and novel light sources.Opt. Express22, 11995-12006 (2014)..

Chen, X., Sun, T. Y.&Wang, F. Lanthanide-based luminescent materials for waveguide and lasing.Chem. - Asian J.15, 21-33 (2020)..

Beier, H. T., Coté, G. L.&Meissner, K. E. Whispering gallery mode biosensors consisting of quantum dot-embedded microspheres.Ann. Biomed. Eng.37, 1974-1983 (2009)..

Shopova, S. I. et al. Microsphere whispering-gallery-mode laser using HgTe quantum dots.Appl. Phys. Lett.85, 6101-6103 (2004)..

Gargas, D. J. et al. Whispering gallery mode lasing from zinc oxide hexagonal nanodisks.ACS Nano4, 3270-3276 (2010)..

Bhattacharya, S. et al. Temperature dependence of whispering gallery modes of quantum dot-doped microbottle resonators.J. Lumin.221, 117050 (2020)..

Pang, S., Beckham, R. E.&Meissner, K. E. Quantum dot-embedded microspheres for remote refractive index sensing.Appl. Phys. Lett.92, 221108 (2008)..

Charlebois, M. et al. Toward automatic label-free whispering gallery modes biodetection with a quantum dot-coated microsphere population.Nanoscale Res. Lett.5, 524-532 (2010)..

Zhi, Y. et al. Refractometric sensing with silicon quantum dots coupled to a microsphere.Plasmonics8, 71-78 (2013)..

Lane, S. et al. Protein biosensing with fluorescent microcapillaries.Opt. Express23, 2577-2590 (2015)..

Liu, H. Z. et al. Whispering gallery mode laser from carbon dot-nacl hybrid crystals.ACS Appl. Mater. Interfaces9, 18248-18253 (2017)..

Li, X. J. et al. Stable whispering gallery mode lasing from solution-processed formamidinium lead bromide perovskite microdisks.Adv. Optical Mater.8, 2000030 (2020)..

Wang, S. et al. Solution-phase synthesis of cesium lead halide perovskite microrods for high-quality microlasers and photodetectors.Adv. Optical Mater.5, 1700023 (2017)..

Liu, X. F. et al. Periodic organic-inorganic halide perovskite microplatelet arrays on silicon substrates for room-temperature lasing.Adv. Sci.3, 1600137 (2016)..

An, Y. H. et al. Color-tunable photoluminescence and whispering gallery mode lasing of alloyed CsPbCl3(1-x)Br3xmicrostructures.Adv. Mater. Interfaces7, 1902126 (2020)..

Zhizhchenko, A. et al. Single-mode lasing from imprinted halide-perovskite microdisks.ACS Nano13, 4140-4147 (2019)..

Das, S., Gholipour, S.&Saliba, M. Perovskites for laser and detector applications.Energy Environ. Mater.2, 146-153 (2019)..

Li, S. Q. et al. Water-resistant perovskite nanodots enable robust two-photon lasing in aqueous environment.Nat. Commun.11, 1192 (2020)..

Wang, L. et al. 2D-material-integrated whispering-gallery-mode microcavity.Photonics Res.7, 905-916 (2019)..

Ren, T. H. et al. Whisper gallery modes in monolayer tungsten disulfide-hexagonal boron nitride optical cavity.ACS Photonics5, 353-358 (2018)..

Li, J. T. et al. Single mode ZnO whispering-gallery submicron cavity and graphene improved lasing performance.ACS Nano9, 6794-6800 (2015)..

Ilchenko, V. S. et al. Whispering gallery mode diamond resonator.Opt. Lett.38, 4320-4323 (2013)..

Schell, A. W. et al. Three-dimensional quantum photonic elements based on single nitrogen vacancy-centres in laser-written microstructures.Sci. Rep.3, 1577 (2013)..

Chen, Y. Z. et al. Refractive index sensors based on Ti3C2TxMXene fibers.ACS Appl. Nano Mater.3, 303-311 (2020)..

Klusmann, C. et al. Hybridizing whispering gallery modes and plasmonic resonances in a photonic metadevice for biosensing applications.J. Optical Soc. Am. B34, D46-D55 (2017)..

Park, J. et al. Titanium dioxide whispering gallery microcavities.Adv. Optical Mater.2, 711-717 (2014)..

Gramotnev, D. K.&Bozhevolnyi, S. I. Nanofocusing of electromagnetic radiation.Nat. Photonics8, 13-22 (2014)..

Yan, R. X. et al. Nanowire-based single-cell endoscopy.Nat. Nanotechnol.7, 191-196 (2012)..

Shambat, G. et al. Single-cell photonic nanocavity probes.Nano Lett.13, 4999-5005 (2013)..

Li, Y. C. et al. Living nanospear for near-field optical probing.ACS Nano12, 10703-10711 (2018)..

Gather, M. C.&Yun, S. H. Single-cell biological lasers.Nat. Photonics5, 406-410 (2011)..

Gather, M. C.&Yun, S. H. Lasing fromEscherichia colibacteria genetically programmed to express green fluorescent protein.Opt. Lett.36, 3299-3301 (2011)..

Karl, M. et al. Single cell induced optical confinement in biological lasers.J. Phys. D: Appl. Phys.50, 084005 (2017)..

Vannahme, C. et al. Single-mode biological distributed feedback laser.Lab Chip13, 2675-2678 (2013)..

Camposeo, A. et al. Physically transient photonics: random versus distributed feedback lasing based on nanoimprinted DNA.ACS Nano8, 10893-10898 (2014)..

Hales, J. E. et al. Virus lasers for biological detection.Nat. Commun.10, 3594 (2019)..

Kwok, S. J. J. et al. Multiplexed laser particles for spatially resolved single-cell analysis.Light. Sci. Appl.8, 74 (2019)..

Martino, N. et al. Wavelength-encoded laser particles for massively multiplexed cell tagging.Nat. Photonics13, 720-727 (2019)..

Lv, Z. et al. Intracellular near-infrared microlaser probes based on organic microsphere-SiO2core-shell structures for cell tagging and tracking.ACS Appl. Mater. Interfaces10, 32981-32987 (2018)..

Schubert, M. et al. Lasing in live mitotic and non-phagocytic cells by efficient delivery of microresonators.Sci. Rep.7, 40877 (2017)..

Subramanian, S., Vincent, S.&Vollmer, F. Effective linewidth shifts in single-molecule detection using optical whispering gallery modes.Appl. Phys. Lett.117, 151106 (2020)..

Frustaci, S.&Vollmer, F. Whispering-gallery mode (WGM) sensors: review of established and WGM-based techniques to study protein conformational dynamics.Curr. Opin. Chem. Biol.51, 66-73 (2019)..

Vollmer, F.&Yu, D. S.Optical Whispering Gallery Modes for Biosensing(Springer, Cham, 2020).

Baaske, M. D.&Vollmer, F. Optical observation of single atomic ions interacting with plasmonic nanorods in aqueous solution.Nat. Photonics10, 733-739 (2016)..

Kim, E., Baaske, M. D.&Vollmer, F. In situ observation of single-molecule surface reactions from low to high affinities.Adv. Mater.28, 9941-9948 (2016)..

Kim, E., Baaske, M. D.&Vollmer, F. Towards next-generation label-free biosensors: recent advances in whispering gallery mode sensors.Lab Chip17, 1190-1205 (2017)..