In 1963, Dr. Green established the 3T3 line which was ideally suited to the study of oncogenic viruses. Three years later, the Green Lab discovered that human-mouse cell hybrids selectively lose human chromosomes, leading to the basis for the cloning of human genes associated with genetic diseases. In 1974, Dr. Green developed the first cell line able to differentiate into adipocytes in culture. This cell line became the basis for most studies on the factors that control adipogenesis. In that same year, the Green Lab discovered a method for the cultivation of human keratinocytes, the main cell type of the epidermis. This led to the development of the first therapeutic use of cultured cells, which has since saved thousands of lives all over the world. In 2002, Dr. Green started working on human embryonic stem cells. He subsequently defined the conditions that permit differentiation of the embryonic stem cells into keratinocytes and studied the factors that control this differentiation.