Interactomics aims at identifying and characterizing in a comprehensive way the complete set of protein-protein interactions that occur within a cell, tissue, or organism. In this chapter, we cover the most relevant experimental and computational approaches that are used in the field to assess the interactome of a specific protein or of all the proteins in a defined compartment. We address their applicability as well as their advantages and disadvantages. We then describe the different databases available to researchers interested in dissecting protein-protein interactions and finally briefly summarize the several attempts that have been made to identify the human interactome, i.e., the complete set of protein interactions that occur within a human cell.