A photon is a tiny particle of light. Every ray of sunshine streaming through your window, every glow from a lightbulb, and every flash from a firefly is made of countless photons traveling at incredible speed.

Scientists discovered that light behaves both like a wave (rippling across space) and like a stream of particles. Each photon carries a specific amount of energy, which determines its color. Red photons carry less energy, while blue and violet photons carry more. This is why a hot flame glows blue at its center: those photons pack more energy than the red and orange ones at the edges.

Photons are massless, meaning they have no mass, yet they can push against objects. This might sound impossible, but engineers have designed experimental spacecraft with giant sails that catch photons from the Sun, using light itself for propulsion through space.

When you see a rainbow, you're watching millions of photons of different energies separated by water droplets in the air. When you look at a distant star, photons that began their journey years ago are finally reaching your eyes. Every photon tells a story about where it came from and what created it.