Optical microcavities confine light to small volumes by resonant recirculation. Because of their ultrahigh quality factors (Q) and small mode volumes (Vm), optical microcavities have attracted strong research interests for their unique property of significantly enhancing light–matter interaction.1 In recent decades, optical microcavities have become cornerstones for a wide range of studies and applications, including nonlinear photo-nics2–4, non-Hermitian5,6 and chaotic physics7,8, cavity quantum electrodynamics9,10 and cavity optomechanics11, optical sensing12,13, and in particular, microlasers14,15. Optical cavities serve as an essential building block of lasers from the date of their birth by enhancing photon–material interactions and providing optical feed-backs. In the past decades, along with the development of various nanofabrication and packaging techniques, microcavities with ultrahigh quality factors and minia-tured sizes have enabled low-threshold and high-coherence lasers down to chip scale. Meanwhile, laser physics and applications have been greatly advanced by exploiting the spectral, temporal, and spatial degrees of freedom of microcavities and their rich interactions with various materials. Nowadays, microcavity-based lasers provide not only indispensable tools in applied researches such as biochemical sensing/imaging and high precision spectroscopy, but also practical devices including atmo-spheric monitors or smart phone and computer chips that have the potential for entering diverse aspects of people's daily life.