Ageing is the most complex phenotype currently known, since it becomes manifest in all organs and tissues, affects an organism's entire physiology, impacts function at all levels and increases susceptibility to all major chronic diseases. Insight into the molecular and cellular targets of the ageing process would offer the unprecedented opportunity to postpone and prevent some, if not all, of its deteriorative aspects by preventive and therapeutic means. Thus far, our understanding of the causes of ageing is limited. To an important extent this is due to our inability, in the past, to study ageing systems. Instead, ample information has been gathered about individual cellular components at various ages, but this has not allowed a clear understanding of the integrated genomic circuits that control mechanisms of ageing, survival and stress responses. With the emergence of functional genomics, we finally have the opportunity to study ageing in a comprehensive manner, as a function of the dynamic network of genes that determines the physiology of an individual organism over time.