Post-translational modifications (PTMs) are chemical alterations to a protein following translation, regulating stability and function. Reversible phosphorylation is an example of an important and well studied PTM involved in a number of cellular processes. SUMOylation is another PTM known to modify a large number of proteins and plays a role in various cellular processes including: cell cycle regulation, gene transcription, differentiation and cellular localisation. Therefore, understanding the role of SUMOylation in cell biology may allow the development of more efficient models, important in streamlining the drug discovery process. This review will focus on protein SUMOylation and its role in stem cell and somatic cell biology.