Dr. Jaenisch received his M.D. from the University of Munich in 1967. He then undertook two years of postdoctoral research on the replication and transcription of the Escherichia coli phages M13 and Phi174 at the Max Planck Institute for Biochemistry, followed by a further two years studying the replication, transcription, and transformation of the SV40 virus in Dr. Arnold Levine's lab in the Department of Biochemistry at Princeton University. He spent an important eight months as a visiting fellow in the laboratory of Dr. Beatrice Mintz at the Fox Chase Institute for Cancer Research in Philadelphia, learning micromanipulation techniques and investigating the in vitro cultivation and reimplantation of isolated mouse embryos. He continued to collaborate with Dr. Mintz during his assistant research professorship at The Salk Institute in La Jolla, California, during which time they published their results on the generation of the first transgenic mice. He then spent seven years as the Head of the Department of Tumor Virology at the Heinrich Pette Institute for Experimental Virology and Immunology at the University of Hamburg, continuing his work on genetic disease, cancer, mammalian development, and the interaction of viruses with early mammalian embryos. In 1984 he became a founding member of the Whitehead Institute for Biomedical Research, where today he holds the position of Professor of Biology, Massachusetts Institute of Technology, and is world renowned for his work on nuclear transfer (NT), as well as cancer, epigenetic regulation, and mammalian development.