Photosynthesis occurs in plants and certain types of algae, in the structures known as chloroplasts. The leaves of a plant are the primary location where photosynthesis takes place, with very little occurring in the stems or branches.
The mesophyll cells are part of the structure of a leaf. These cells contain chloroplasts and are where photosynthesis happens. A green pigment, known as chlorophyll, is specifically involved in photosynthesis. Part of the structure of a chloroplast is known as a thylakoid. The membrane of the thylakoid has chlorophyll built into it. Chlorophyll absorbs red and blue light, while reflecting green light. This reflected light is what reaches the eyes, giving chlorophyll its green color.