The maser, older sibling of the laser, has been relatively obscure due to its demanding operating condition of the high-vacuum system and cryogenic refrigeration. Despite this, it has found application in ultrasensitive magnetic resonance spectroscopy, astronomy observation, space communication, radar, and high-precision clocks. Room-temperature solid-state masers are highly desirable. Recently a research group was successful in developing a continuous wave solid-state diamond maser. This demonstration unlocks the potential of room-temperature solid-state masers for use in a new generation of microwave devices. This seminar is a brief account of the current developments in the solid-state masers.