Take a deep breath. The oxygen molecules that your lungs are absorbing are the result of one of nature’s most enigmatic processes: photosynthesis, or in this case, the conversion of sunlight, water and carbon dioxide into sugar and oxygen.

On a molecular level, photosynthesis starts when pigments in plant and algal tissues capture light energy to tear water molecules into their building blocks: oxygen and hydrogen. The oxygen gas is released and the hydrogen attaches to carbon dioxide molecules to create an energy-rich sugar that the plant or algae uses to feed itself. Thousands of molecular machines called enzymes help make these chemical reactions possible.

Photosynthesis helps sustain life here on Earth, but what might it look like elsewhere in the universe? Scientists think that light-absorbing pigments on other planets would evolve to suit the wavelength of light from the star in their planetary system. Instead of green, alien plant or algae equivalents could be red, blue or even reflect a color we can’t see and appear to be black.