For the first time in humanity, we get a holistic assessment of how many cell types/states there are, what programs are shared and distinct, and provide clues as to what the function of every cell is. It can also provide insight into which cells are responsible for pathology e.g. a cancer stem cell, pathological immune cell etc. This is exemplified in recent high profile publications, and the ambitions of the Human Cell Atlas (humancellatlas.org). I will discuss the technique we employ (CEL-seq2), considerations in the design, execution, QC and interpretation of scRNA-seq experiments. Then using an example of ~1,500 index-sorted haematopoietic stem and progenitor cells, demonstrate the power of our novel approach to unmask some of the underlying trajectories in haematopoiesis.