Human breast cancer (BC) is one of the leading causes of death for women worldwide, and is characterized by a group of highly heterogeneous lesions. The morphological and biomolecular heterogeneity of BC cells, accompanied by dynamic plasticity of the BC microenvironment and the presence of stem-like cells, make tumor categorization an urgent and demanding task.The major limitations in BC research include the high flexibility rate of breast cancer stem cells (BCSCs) and the difficulty of their identification. Improved profiling methods and extensive characterization of BCSCs were recently presented in BMC Cancer, highlighting that the majority of BC cells had a luminal EpCAMhigh/CD49f+ phenotype, and identification of CD44high/CD24low subpopulation of cancer stem cells significantly improves the flow cytometry measurement of BCSCs with higher stem/progenitor ability.Future developments in single-cell omics will potentially revolutionize cancer biology and clinical practice, providing better understanding of BC heterogeneity, how BCSCs evolve, and which BC cells to target to avoid drug resistance.Please see related research published in BMC Cancer: http://www.biomedcentral.com/1471-2407/13/289/abstract.