We start out as a clump of generic cells, but at some point, cells have to start taking on special features and functions. As cells choose their fate, they go through a process that specializes their roles, called differentiation.
Learn more about differentiation from the video, which is described by some scientists as "noisy," because of the way DNA is transcribed at this time. Most of our genes get transcribed into proteins, and different kinds of cells have different protein requirements. Before cells have specialized, however, they often transcribe a bunch of random stuff, instead of making a specific set of genes, like a differentiated cell needs. The mess that gets generated has been called noise, as the video explains.