English: Figure 2. Pluripotent stem cells differentiate down lineages (solid arrows) to give rise to various cell types. (a) Reprogramming (dashed arrows) is where fibroblasts revert back to pluripotency. (b) During transdifferentiation, cells transform into other cells by swapping lineages. This may occur either directly (dashed arrow) or involving a dedifferentiation step (bold arrow). (c) Dedifferentiation is the process by which mature cells regress within its own lineage which often allows it to proliferate.