Living metal
From Tardis Wiki, the free Doctor Who reference
Living metal was a metal which was able to grow. It was discovered by Professor J.P. Kettlewell. He used it to create the Experimental Prototype Robot K1. (TV: Robot)
Validium, a Time Lord creation, was also described as a living metal. (TV: Silver Nemesis)
The Architectural Reconfiguration System of The Doctor's TARDIS was built from a type of living metal. (TV: Journey to the Centre of the TARDIS)