It is becoming apparent that embryonic and fetal cells have a complex system to integrate nutritional signals from their environment and adapt their development accordingly to ensure survival. Human diets are comprised of complex mixtures of protein, fats, carbohydrate and vitamins. The full impact of inappropriate programming of metabolic regulation is only just beginning to be appreciated. The available evidence suggests that nutrient sensing regulatory systems are present in many critical tissues during early development. It remains to be seen whether they play an important part in establishing homeostatic control mechanisms early in life.