摘要： A laser is a device that emits strong coherent light through a process of light amplification by stimulated emission of radiation. The theoretical foundation for the laser was established by Albert Einstein theorizing on the existence of stimulated emission in 1916. The first laser was built by Theodore Maiman in 1960 based on the theoretical work of Charles Townes and Arthur Schawlow. The invention and continuous development of the laser has revolutionized science, technology, and industry. Miniaturization of lasers has been promoting the development and application of laser technology. For example, compact semiconductor lasers have become an integral part of our everyday life. With the development of micro- and nanofabrication technology, including both top-down and bottom-up techniques, the dimensions of lasers have been shrunk down to micro- and nanoscale. With an unprecedented ability to deliver intense coherent light at (sub)wavelength scale, such micro- and nanolasers are promising to trigger the next revolution in the laser and related fields. Indeed, the micro- and nanolasers are or will be unlocking their potential in photonic and optoelectronic applications, such as chemical and biological sensing, laser display and holography, on-chip optical communication and processing, and so on.