Chlorophyll.

http://en.wikipedia.org/wiki/Chlorophyll

Chlorophyll (also chlorophyl) is a green pigment found in cyanobacteria and the chloroplasts of algae andplants.Its name is derived from the Greek words χλωρός, chloros ("green") and φύλλον, phyllon ("leaf").Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to absorbenergy from light. Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. Conversely, it is a poor absorber of green and near-green portions of the spectrum, hence the green color of chlorophyll-containing tissues.Chlorophyll was first isolated by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817.

Chlorophyll and photosynthesis

Chlorophyll is vital for photosynthesis, which allows plants to absorb energy from light.

Chlorophyll molecules are specifically arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts.In these complexes, chlorophyll serves two primary functions. The function of the vast majority of chlorophyll (up to several hundred molecules per photosystem) is to absorb light and transfer that light energy by resonance energy transfer to a specific chlorophyll pair in the reaction center of the photosystems.

 Chlorophyll gives leaves their green color and absorbs light that is used in photosynthesis.

Chlorophyll is found in high concentrations in chloroplasts of plant cells.