Chlorophyll is the green substance in plants that captures energy from sunlight and turns it into food through a process called photosynthesis. It's what makes most plants green: grass, tree leaves, lettuce, and even algae get their color from chlorophyll.

Here's how it works: chlorophyll acts like a tiny solar panel inside plant cells. When sunlight hits it, the chlorophyll absorbs the light's energy (especially red and blue light, which is why it reflects green light back to our eyes). The plant then uses that captured energy to combine water from the soil and carbon dioxide from the air into sugar, which feeds the plant and helps it grow.

Without chlorophyll, plants couldn't make their own food, and without plants making food, animals (including humans) would have nothing to eat. Every time you bite into an apple or munch on a carrot, you're benefiting from the work chlorophyll did.

In autumn, when leaves change color, it's because the chlorophyll breaks down and disappears, revealing the yellow, orange, and red colors that were hidden underneath all along. The green was so dominant during summer that it covered up the other colors.