Photosynthesis is nature’s way of making life from light. Chlorophyll allows a tree to capture photons, extracting a portion of their energy to make the sugars that make it a tree — the raw material for leaves and bark and roots and branches — then releasing the photons at lower wavelengths back into the atmosphere. A tree is a light-catcher that grows life from air.

Although the human mind has puzzled over why leaves fall and change color at least as far back as Aristotle, chlorophyll — which shares chemical kinship with the hemoglobin in our blood — was only discovered and named in 1817, by the French pharmacist-chemist duo Joseph Bienaimé Caventou and Pierre Joseph Pelletier. In a lovely touch of humility that distinguishes, always, the scientist from the explorer — the explorer, so eager to name the lands and landmarks he has “discovered” after himself — they wrote in their landmark paper:

We have no right to name a substance long-known, and to the story of which we have added only a few facts; however, we will propose, without granting it any importance, the name chlorophyll, from chloros, color, and φυλλον, leaf: a name that would indicate the role it plays in nature.

Red maple by Clarissa Munger Badger, who inspired Emily Dickinson. (Available as a print and as stationery cards, benefitting The Nature Conservancy.)

But chlorophyll, which is yet to be fully understood, is not the only pigment in trees. Throughout a leaf’s life, four primary pigments course through its cells: the green of chlorophyll, but also the yellow of xanthophyll, the orange of carotenoids, and the reds and purples of anthocyanins.