Light art or luminism is a visual art form in which light is the main medium of expression. It is an art form in which either a sculpture produces light, or light is used to create a "sculpture" through the manipulation of light, colours, and shadows. These sculptures can be temporary or permanent, and can exist in two distinctive spaces: indoor galleries, such as museum exhibits, or outdoors at events like festivals. Light art can be an interaction of light within an architectural space. Light artists are those that devote all their creative experimentation to light art, some artists experiment with light and neon signage and use light in their practice.