Scientists hope to gather a new understanding of biology by closely examining the fundamental units of life - single cells. Recent technological improvements have now enabled scientists to sequence the genome and the epigenome, i.e. the programming, as well as the transcriptome, i.e. the "current" programming, of single cells. These methods allow us to get a better understanding of cell types, how different cell types interact and change throughout their life. This research has implications in general cell biology, cancer, immunology and infectious diseases.