Photograph by Andrew Syred/Science Photo Library

This scanning electron microscope image reveals the intricate patterning of ancient coccolithophores, microscopic plankton abundant in shallow seas during the Cretaceous period. As these organisms died, their skeletons, called cocospheres, fell by the trillions to the seafloor, forming layer upon layer of calcium carbonate. Millions of years of pressure and heat turned these layers into the chalk we use today in our everyday lives and helped preserved countless fossils from the Cretaceous.