Light. It’s a big part of what may be the most important recipe on the planet. Water and carbon dioxide are other key ingredients. The recipe is for photosynthesis. That’s how plants make the food they need to live and grow.
The word “photosynthesis” means “putting together with light.” That phrase describes what happens in plants. The food-making cells in plants combine water and carbon dioxide. They do it by using light energy. That light energy may come from the Sun. It can also be from an artificial source. A light bulb may do the job, too. Either way, the plant makes sugar. Plants use this sugar, plus nutrients from soil, to make proteins, vitamins, and other things they—and we—need to live.
This is it in a nutshell: Without light energy there would be no sugar. Without sugar there would be no plant life. And without plant life there would be no animals or people.