Photo- and chemical crosslinking of proteins have offered various avenues for studying protein structure and protein interactions with biomolecules. Conventional photoactivatable groups generally lack reaction selectivity toward amino acid residues. New photoactivatable groups reacting with selected residues have emerged recently, increasing crosslinking efficiency and facilitating crosslink identification. Traditional chemical crosslinking usually employs highly reactive functional groups, while recent advance has developed latent reactive groups with reactivity triggered by proximity, which reduce spurious crosslinks and improve biocompatibility. The employment of these residue selective chemical functional groups, activated by light or proximity, in small molecule crosslinkers and in genetically encoded unnatural amino acids is summarized. Together with new software development in identifying protein crosslinks, residue selective crosslinking has enhanced the research of elusive protein-protein interactions in vitro, in cell lysate, and in live cells. Residue selective crosslinking is expected to expand to other methods for the investigation of various protein-biomolecule interactions.