.The last 15 years of the 20th century and the beginning of the 21st century saw spectacular progress in molecular biology. The analysis of spontaneous or induced mutants in man and model species has lead to the identification of the specific function of thousands of genes. Fine mapping of genomes has been a key step in such identification. However, it is now clear that understanding regulatory mechanisms cannot be achieved by studying isolated genes alone, it must focus on the combined and dynamic expression of the entire gene network. Genome sequencing projects have inaugurated a series of new techniques, photographing in real-time the result of genomic expression in different cell types under various physiological or pathological conditions. The analysis and comparison of these specific patterns requires the extensive use of bioinformation tools, already omnipresent in the production and exchange of biological data. Such research is expected to reveal the full functioning of living organisms at all levels of its organization, from the molecules to the whole body. Far from being futuristic projects, the first computational attempts at physiological modelling are already in existence and constitute a clear turning point in our descriptive and predictive approach of biological phenomena.