Photosynthesis is the process by which green plants make food for themselves-and, indirectly, for all animals, including human beings. Without it, life as we know it on this earth would be impossible.
In photosynthesis plants combine water and salts in the soil, and carbon dioxide in the air to build up organic compounds, such as sugar starch and proteins. To do this they use the energy of sunlight, which is absorbed with the help of the green dye in their leaves called chlorophyll.
This process of manufacturing food from what they absorb through their roots and leaves makes green plants the primary food producers in the world. All animals draw their nourishment from them, either by feeding on the plants themselves or by eating other animals that do so. During photosynthesis, which takes place only in daylight, excess oxygen is produced and released into the atmosphere for animals to breathe. After the Second World War, the American scientist Melvin Calvin wrote a book about how plants capture the carbon dioxide in the atmosphere. In 1961 he received the Noble Prize in Chemistry in recognition of his work.