Our most sophisticated knowledge of physics, tells us that light can be a particle or a wave. It is extremely tiny. Its dimension called wavelength, is about a thousand part of a millimeter. It has Energy and Momentum with their characteristic unusual values. Many simple applications of quantum mechanics are in light.
Light emitted by a laser, is one of the most fascinating inventions of our time.
All the knowledge of Einstein's Relativity is based on the critical speed of light.