A green pigment that gives most plants their color and enables them to carry on the process of photosynthesis.

Chemically, chlorophyll has several similar forms, each containing a complex ring structure and a long hydrocarbon tail.

Within the photosynthetic cells of plants the chlorophyll is in the chloroplasts; small, roundish, dense protoplasmic bodies that contain the grana, or disks, where the chlorophyll molecules are located.

Chlorophyll absorbs light in the red and blue-violet portions of the visible spectrum; the green portion is not absorbed and, reflected, gives chlorophyll its characteristic color.

When the amount of chlorophyll decreases, other colors become apparent. This effect is seen every autumn when the leaves of trees "change color".