Stuart Hameroff has jointly developed a theory of quantum consciousness with Roger Penrose. Penrose advanced the idea of a non-computable quantum process in the brain. Initially, Penrose had no very cogent idea as to how the brain would support such a process. Hameroff, whose main career was in anesthetics, developed the theory that microtubules, which are skeletal structures formed of protein within living cells, were suitable to support the necessary quantum activity.