A good way to find out what a cell is doing—whether it is growing out of control as in cancers, or is under the control of an invading virus, or is simply going about the routine business of a healthy cell—is to look at its gene expression. Though a vast majority of cells in an organism all contain the same genes, how those genes are expressed is what gives rise to different cell types—the difference between a muscle cell and a neuron, for example.
source https://phys.org/news/2021-04-swiss-army-knife-genomic.html
