Developmental Biology
How can a single cell, the fertilized egg, give rise to all the specialized cells of an adult? What gives rise to biological form? What is the molecular logic of the pathways that progressively refine cellular identities? How do cells "talk" to one another so as to coordinate their behaviors as embryos develop form and function? How can parts of an organism be regenerated with only the appropriate regions remade, structured identically to the missing ones? How does a stem cell differ from a non-stem cell? How can genetically identical organisms be cloned?