We selected from the literature the first articles describing large-scale protein–protein, epistatic, and chemical–genetic interaction networks for several model organisms (E. coli, S. cerevisiae, S. pombe, the fly D. melanogaster, the worm C. elegans, and human). We illustrate here the timeline in which these studies were conducted with additional information provided in Table 7.1. Y2H, PPIs derived from yeast-two-hybrid; AP-MS, PPIs derived from affinity tag-purification followed by mass spectrometry