A Pleurosigma, a type of phytoplankton in the ocean. Phytoplankton generate more than half of the Earth's oxygen. Harry Taylor/Nikon Small World hide caption

itoggle caption Harry Taylor/Nikon Small World

A flint-knapper makes sharp stone flakes by striking a flint "core" with a hammerstone. Human Origins Initiative hide caption

itoggle caption Human Origins Initiative

Scientists studied the Manduca sexta caterpillar under X-ray and found that when caterpillars walk, their guts move forward first, followed by the rest of their bodies in a rippling movement. Ted Kropiewnicki/Tree of Life Web Project hide caption

itoggle caption Ted Kropiewnicki/Tree of Life Web Project

Paul Greenberg, pictured here with his daughter Tanya, has been fishing striped bass since childhood. He frequently writes about fish for The New York Times. Courtesy of Paul Greenberg hide caption

itoggle caption Courtesy of Paul Greenberg

The eggs are layered with moist sand to cushion their journey. Share the Beach volunteers use counters to make sure all 127 eggs from this loggerhead nest are accounted for. Debbie Elliott/NPR hide caption

itoggle caption Debbie Elliott/NPR