Plants store energy through the process of photosynthesis by converting sunlight into chemical energy in the form of glucose. During photosynthesis, plants absorb sunlight through their chlorophyll-containing cells in their leaves. This sunlight is then used to convert carbon dioxide from the air and water from the soil into glucose and oxygen. The glucose produced is stored in various parts of the plant, such as roots, stems, and fruits, and serves as an energy source for the plant's growth and metabolism.