Worn-out cells eventually stop dividing

I'm getting too old for this CELLS divide many times throughout their lives. But they cannot do it indefinitely. Once they have reached the limits of their reproductive powers, they enter a state called "senescence", in which they carry on performing their duties but stop making new copies of themselves. For years it was assumed that, apart from their refusal to divide, senescent cells were otherwise identical to their replicating compatriots. There is mounting evidence, though, that this is unt...