Single‐cell technologies are revolutionizing the approach to rare cells

In the last lustrum single‐cell techniques such as single‐cell quantitative PCR, RNA and DNA sequencing, and the state‐of‐the‐art cytometry by time of flight (CyTOF) mass cytometer have allowed a detailed analysis of the sub‐composition of different organs from the bone marrow hematopoietic compartment to the brain. These fine‐grained analyses have highlighted the great heterogeneity within each cell compartment revealing previously unknown subpopulations of cells. In this review, we analyze how this fast technological evolution has improved our understanding of the biological processes with a particular focus on rare cells of the immune system. The March 2016 issue contains a Special Feature on Cutting‐edge single‐cell genomics and modelling in immunology. The recent advent of single‐cell genomics has offered unprecedented possibilities for hypothesis‐independent characterization of cellular heterogeneity and regulatory states. At the same time, the vast datasets produced by these techniques have highlighted the need for new bioinformatics tools to utilize the contained information to the fullest. In this Special Feature, both the experimental methods for producing such data as well as selected modelling approaches are reviewed, with focus on the applications on the study of the immune system. Immunology and Cell Biology thanks the coordinators of this Special Feature ‐ Tapio Lönnberg and Valentina Proserpio ‐ for their planning and input.