Boolean Networks Take On Cellular Aging
A skin cell is like a ball rolling across hilly terrain. When young, it hops easily between shallow dips, but with age the landscape changes: some dips grow deeper, others flatten out, and the ball gets stuck in the same hollow more and more often. That hollow is a stable state of the cell, one in which the genes run an "old" program.
Biologists spent a long time searching for which genes make a cell age.