<p>Tumor is generally believed to originate from a single cell, which develops into a genetically heterogeneous population after continuous cell divisions under the principle of “survival of the fittest”. Tumor evolution is a dynamic process, and reconstruction of the disappeared history is challenging but crucial for both understanding the mechanism and personalized therapy. Genetic alterations can be used as molecular clues to tumor evolution, with somatic mutations as a key tracer. Although bulk-level sequencing of a large number of tumor specimens has provided useful information on the mutational landscape, it is not easy to utilize such data for evolutionary history study. This is because bulk-level mutation prevalence may be confounded by various factors, such as tumor purity, copy number alterations, and more severely, the overlapping of prevalence ranges for mutations from similarly sized subclones. Single-cell mutational profiling overcomes such challenges, enabling precise identification of co-mutation groups and tumor subclones. This further enables successful reconstruction of tumor evolution, even for a solid tumor sample collected at a single time point. Technical and analytical advancements in single-cell profiling, such as mutation calling from single-cell RNA-Seq or spatial transcriptomic data, will provide further insights into tumor evolution and cancer treatment.</p>