Gangers were developed to work in environments too dangerous for people. Controlled remotely by a human operator they soon saved lives and money and most believed a Ganger was simply a tool, little more than a fork-lift truck. But the Doctor immediately recognized they were much more, insisting they had a mind and a soul.
Gangers are formed from a type of flesh; once a reading has been taken it can be manipulated into anything, even replicating a living organism.
When the Doctor visited a mine run by Morpeth Jetsan a storm struck and "hardwired" the Gangers. Normally, it’s claimed that when the link is broken between the operator and the Ganger, the Ganger reverts to "pure flesh." But the link has been broken and this time the Gangers have evolved. Something new is being created. Something living, something exciting. And something very, very dangerous.