Optical microresonators have been one of the most active and exciting research topics in the photonics community in recent years. By confining light in both spatial and time domain, optical microresonators serve as an indispensable platform for significantly enhancing light–matter interaction and controlling light fields at the micro- and nano-scale. These capabilities make optical microresonators important tools for a wide range of applications, including sensing, metrology, communication, and quantum computing.