Millicent Ellis Selsam was born in New York City on May 30, 1912. She became interested in biology during her high school years, and went on to study biology at Brooklyn College. She was then offered a fellowship teaching at Columbia University while completing an M.A. in botany. After she received her M.A., she taught high school science. In 1946 she left teaching to write science discovery books for children. Her first published book was Egg to Chick (1946), which started a science series of "I Can Read" books for Harper. Over the course of her career she wrote approximately 130 children’s books. Her books received many awards, including the Thomas Alva Edison Award for the best juvenile science book, ''Biography of an Atom'' (1965).