Stanley Cohen (1922 - present) received half of the 1986 Nobel Prize for Physiology or Medicine for his research on chemicals called growth factors that influence the development of nerve and skin tissues. Cohen isolated the nerve growth factor (NGF), a natural substance that his fellow Nobel Laureate Rita Levi-Montalcini had shown stimulated the growth of nerve cells and fibers. Cohen found another growth factor in chemical extracts that contained NGF. He discovered that this substance caused the eyes of newborn mice to open and their teeth to erupt several days sooner than normal. Cohen named this substance epidermal growth factor (EGF), and he later purified it. He and his coworkers found that EGF influences a great range of developmental events in the body and discovered the mechanisms by which EGF is taken into and acts upon cells.