Abstract: If light bosons exist in nature, they will spontaneously form ‘clouds’ around black holes by extracting rotational energy from rotating massive black holes through superradiance, a classical wave amplification process that has been studied for decades. The superradiant growth of the cloud sets the geometry of the final black hole, and the black hole geometry determines the shape of the cloud. Hence, both the black hole geometry and the cloud encode information about the light boson. I will discuss the light boson detection and constraints that could be obtained through gravitational-wave observations.