Mesh emitters at work in a kid toys scene.
In Arion light sources can be either the environment (physical sky or image-based lighting) or emitter materials applied to any object in the scene that will become a light source and illuminate the entire scene.
Mesh emitters can be of any shape and any number of vertices, but trying to keep emitters as simple as possible should be kept in mind when possible.
All you have to do to create an emitter, is to apply an emitter material on the desired object. On a default new RandomControl material, simply turn the default BSDF layer into an emitter layer, apply the material on the object and let it shine. Adjust its color, power or spread if necessary.
Parts of the bike were turned into emitters materials to create this image.