This volume contains the papers and discussion presented at the Fourth Conference on the Biology of Normal and Atypical Pigment Cell Growth (November, 1957). It is fittingly dedicated to Myron Gordon, who was the creative force behind these conferences. Pigment formation and pigment-forming cells are presented from the viewpoint of the embryologist, histologist, geneticist, endocrinologist, physiologist, cytochemist, comparative pathologist, biochemist, biophysicist, and physician. While this is not a textbook, the extensive bibliographies and discussion will acquaint the reader with earlier basic research. This volume should be read by everyone working in the field of pigmentation for the viewpoints of investigators with varying scientific backgrounds. It is almost a necessity for anyone now entering the field of pigmentation, since it will provide a solid orientation regarding previous research and current concepts in this field.