The Sun heats up our landmasses, oceans, and the air. It gets water to evaporate to create clouds. When the water vapor is cooled, small water droplets are formed inside the clouds, and these will fall down as rain and provide water to plants, animals, and humans. The plants are using sunlight to convert carbon dioxide (CO2) and water to carbohydrates. At the same time, they release oxygen that humans need to breathe. This process occurring in plants is called photosynthesis, and the plants need the carbohydrates to grow, just like humans and animals.