Bill Breed was born in the UK and, after completing school, worked as a field assistant at The Edward Grey Institute of Field Ornithology at Oxford University. He then studied zoology at Aberdeen University and returned to Oxford University to carry out his doctoral studies on the reproductive biology of the field vole (Microtus agrestis). This work resulted in several publications including one in Nature. He did a postdoctoral fellowship at UCLA, returning to the UK for his second postdoctoral fellowship at Birmingham University, working on determining the mechanism of action of the intrauterine contraceptive device. He migrated to Australia in 1973 to take up a lectureship in anatomy at The University of Adelaide where he worked until his retirement in 2015. For many years, he has focused on light and electron microscopical studies of sperm and eggs, their interaction at fertilisation, and the development of early embryos of Australian native mammals.