Virtual reality is a technology to mimic real objects and environments. In this manuscript, the author introduces a basic concept of virtual reality as well as metaverse, which is a recent trend. In medical and biological engineering, virtual reality is used for basic and application studies to reveal basic biological functions and support medical treatment. The virtual reality system consists of display system, input system and simulation. The author explains the difference of the two types of head mounted displays and introduces tips for a beginner of virtual reality to develop a system.