On-chip quantum optics harnesses the power of light at the quantum level, integrated onto miniaturized photonic circuits. This cutting-edge field enables the creation of compact and scalable devices for manipulating individual photons and their quantum states, as we strive to utilize these quantum characteristics of light for significantly better performance in diverse technologies. By integrating quantum light sources, detectors, and processors on a chip, it paves the way for revolutionary applications in quantum computing, secure communication, and ultra-sensitive sensing.