From a Single Cell: Well, by and large, this does not apply to individual people. Physical constraints are generally a bugger, and Healing Factor is about the best one can do. Otherwise, time to dig out the backups.
Civilizationally, on the other hand, this is what the Civilization-Backup Ships are for, vast collections of databases and genomes and mind-states and other such things that spend most of their time out in the deep, deep black between star systems – waiting on Proceed Unless Cancelled programs to head out for distant pastures and recreate the Empire’s civilization well away from whatever destroyed the original.
Just in case of existential risks and threats, belike.