Glucose is a simple sugar with the formula C6H12O6. It is a monosaccharide, meaning that it is the most basic unit of carbohydrates. Glucose is the primary source of energy for most organisms, including plants and animals. Plants produce glucose through photosynthesis, while animals obtain it by consuming plants or other animals. Glucose is broken down by cells in a process called cellular respiration, which produces energy in the form of ATP (adenosine triphosphate).