George Gey paid his way through a biology degree at the University of Pittsburgh by working as a carpenter and mason, and he could make nearly anything for cheap or free. During his second year...

They also knew that there was a string of DNA at the end of each chromosome called a telomere, which shortened a tiny bit each time a cell divided, like time ticking off a clock....

Only cells that had been transformed by a virus or a genetic mutation had the potential to become immortal.