Some 3.5 billion years ago the chlorophyll molecule first appeared in minute organisms called cyanobacteria, enabling them to capture light energy from the Sun. Eventually, enough free oxygen was released into the atmosphere for life to become possible for land plants and animals—and ourselves. We have these tiny oxygen-producers to thank for much of the life that exists on the Earth today. The works in this section feature both fossil and living domes (stromatolites) created by these cyanobacteria.