Throughout their development, oocytes, embryos and foetuses are sensitive to changes in their environment. Such changes can have an immediate effect on development and/or can impart a legacy on the subsequent development of these structures for their remaining pre- and post-natal lives. Of the various environmental factors that can affect development, alterations in nutrient supply, either through modifications to the maternal diet, or the composition of oocyte or embryo culture media, have been most studied. Not only do alterations in nutrient supply have long-term effects on gross characteristics such as size and growth, they also affect the integrity of all tissues and organs of the body, contributing to the lifelong health and well-being of the resultant offspring. Increasingly, research in this area is focussing less on descriptions of the impact of altered nutrition on later development, but instead on gaining underlying mechanistic understanding of how nutrient supply programmes development. It is important to distinguish consequences of nutrient programming that merely enable the organism to adapt to a changed environment, from those that programme potentially harmful and irreversible long-term changes.