A cell can be described as a synergistic ensemble of biological entities (mRNA, proteins, ncRNA, metabolites, etc) interacting with each other, whose collective behaviour causes the observed phenotypes. A great research effort is ongoing in identifying and mapping the network of interactions among biomolecules in mammalian species. The idea of harnessing this network to understand human diseases at the molecular level, and possibly to find suitable drugs for their treatment, is fascinating but still unfulfilled. We will show how it is possible to harness experimental data on human cells and tissue to identify the gene regulatory networks among tens of thousands of genes, and how to use this information to analyse the modular structure of the cell and predict the function of each gene. Moreover, we will show how using these data it is also possible to identify a suitable drug, or a combination of drugs, that can restore the physiological behaviour of the affected pathways in human diseases.