Cancer is caused by mutations in the genome. Conceptually, the development of a cancer can be driven by mutations in genes that cause abnormally increased activation of a process; these genes are called proto-oncogenes or oncogenes, including c-MYC, RAS or BCR-ABL. However, neoplastic transformation can be prevented in cells by so-called tumour suppressors, including p53 and RB. I will describe how the concept of tumour suppression was discovered and describe some of the research that led to the discovery of tumour suppressor genes and their functions.