Potter wanted to study the early stages of tumor growth, but these tumors only grew in animals. In 1986, Richard Nordan, a graduate student in Potter’s laboratory found that the tumors could be grown in tissue culture, if they were grown in liquids from cultured white blood cells called macrophages. Nordan identified the component in the liquid as interleukin-6, which is involved in the growth and differentiation of normal white blood cells. Potter and Nordan had discovered a way to grow tumors in the laboratory and a new tool for scientists of many specialities.