Until recently, classical genetics and biochemistry were the main techniques used to investigate how organisms develop, reproduce, behave and age. But with the availability of complete genome sequences new approaches are emerging. Complete sets of proteins — 'proteomes' — can be predicted from genome sequences and used to characterize protein functions globally. For example, through the large-scale identification of physical protein–protein interactions, comprehensive protein interaction maps are being generated. And these maps might help us to understand the processes that control the biology of living organisms.