This chapter discusses the technical and conceptual approaches for lineage tracing cells in liver development, homeostasis, and disease. Tracing cells for mosaic expression of a transgene or mutated gene, or for random inactivation of an X‐linked gene, enabled investigators to identify patches of mutated cells surrounded by non‐mutated cells within developing tissues or liver regenerative nodules. The use of bacteriophage cyclization recombinase (Cre) to genetically mark cells and their progeny has rapidly become the gold standard in lineage tracing experiments. The control of Cre expression in space is usually achieved by constructing transgenes that drive Cre transcription under control of transcriptional regulatory regions that are specifically active in the precursor cell population. Single‐cell methods have considerably expanded our potential to investigate gene expression during cell fate changes. Single‐cell RNA sequencing, followed by classification of the cells based on their transcriptomic profile can identify subgroups of cells within a heterogeneous population.