During development, cells sequentially lose their ability to differentiate into other cell types and become committed to different cellular states. This process can be described as a landscape in which the valleys are canalized one by one. This process of canalization is understood in terms of dynamical systems of interacting cells. In fact, as cells with oscillating gene expression proliferate and interact with each other, they differentiate into other expression states. Cells with oscillatory gene expression have pluripotency, either to replicate the same state or to differentiate into other cellular states, whereas cells that differentiate and lose their oscillations of expression simply replicate themselves, that is, they are committed. The proportion of each cell type is robust to changes in initial conditions and noise perturbations. Differentiation by protein expression dynamics is further stabilized by a feedback process of epigenetic modifications, such as DNA modification. The irreversibly differentiated cell state can be initialized to a pluripotent state by restoring an oscillatory state by forcing the expression of multiple genes from the outside, known experimentally as reprogramming.