The cover image of the American Laboratory April issue was DDT (dichlorodiphenyltrichloroethane). It was done with purified DDT crystals forming (spherulites) from a melt. This organochlorine insecticide can be considered the pesticide of the greatest historical significance, due to its effect on the environment, agriculture, and human health. It was used successfully during World War II to control malaria and typhus among civilians and troops. In 1962, biologist Rachel Carson catalogued the environmental impacts of the indiscriminate spraying of DDT in her book, Silent Spring. Publication of the book eventually led to the banning of DDT in the U.S. Thank you to Michael W. Davidson, Director of the Optical Microscopy Division of the National High Magnetic Field Laboratory, Tallahassee, FL, U.S.A., for providing this cover image.