The process of cancer initiation largely remains a black box. In aged non-cancerous organs, many cells will have already acquired common oncogenic drivers such as TP53 mutations, yet the majority will not give rise to cancer. Whilst identifying and characterizing the precancerous clone(s) that are destined to become cancer is technically challenging, it could be key to early diagnosis and prevention of cancer. Although many transgenic reporter mouse models can trace the entire lineage of cells carrying oncogenic drivers, they often struggle to distinguish precancerous cells from the majority of labelled cells that do not initiate cancer.