The paintings of the abstract expressionist artist Sam Francis contain vivid biomorphic forms. One influence for Francis may have been microscopic images of biological tissues he observed in premedical courses prior to becoming an artist. Using two morphometric measurements common in cell biology, the authors show that forms in Francis’s paintings are statistically similar to cells in biological tissues that resemble his paintings. This study highlights specific similarities between forms in Francis’s paintings and biology. It also presents a novel application of biological morphometrics that could help clarify the creative process and psychological appeal of Francis and other “organic” artists.