The last half a century has witnessed rapid advances in our understanding of genetics and human biology. From James Watson and Francis Crick’s discovery of the structure of DNA in 1953 and the first officially sanctioned human gene therapy trial in 1990, to the completion of the Human Genome Project in 2003 and the aspiration to make a $1000 human genome a reality, our understanding of the role genes play in the development of disease and other phenotypes is rapidly increasing. The results of the ‘genetic lottery’ are arbitrary and they are often tragic, both for the victims themselves and their loved ones and families. This chapter surveys some of the current knowledge of the role genes play in different disorders, and potential for developing new biomedical technologies to improve human health.