The fact that light can exert a pressure on matter suggests it is made of particles called photons.

Here's why:

* Wave-Particle Duality: Light exhibits both wave-like and particle-like properties. While it can behave as a wave (like in interference and diffraction), it also interacts with matter as if it were made of tiny packets of energy called photons.

* Photons and Momentum: Photons, although massless, carry momentum. When a photon collides with matter, it transfers its momentum, resulting in a force and a pressure. This is the fundamental principle behind the phenomenon of light pressure.

The concept of light pressure was first proposed by James Clerk Maxwell in the 19th century and was experimentally confirmed by Lebedev in 1900.