 Life begins when a fertilised egg divides to form new cells which in turn also divide. Initially these cells look identical but over time they begin to change. In a process regulated by our genes some go on to form the heart and others for example the brain. What are the mechanisms that enable a single cell to become a complex organism? This is one of biology's great questions and one which the research of Christiana Nuslan-Volhar has helped to resolve. Her work has allowed us to identify the genes that regulate the development of living organisms shedding light on broad areas of biology and medicine. In the 1970s she began to study the developmental genetics of mutant fruit fly embryos and was able to identify the genes that regulate their complete development. Later she focused her research on the key developmental regulators invertebrates using a new model organism the zebrafish. Her discoveries opened different lines of research. Some of them in the field of medicine which for example have led to a better understanding of the causes of anomalies in human embryonic development.