In the novel, renegade biotechnologist Vergil Ulam creates simple biological computers based on his own lymphocytes. Faced with orders from his nervous employer to destroy his work, he injects them into his own body, intending to smuggle the ‘noocytes’ (as he calls them) out of the company and work on them elsewhere. Inside Ulam’s body, the noocytes multiply and evolve rapidly, altering their own genetic material and quickly becoming self-aware. The nanoscale civilization they construct soon begins to transform Ulam, then others. The people who are infected start to find that genetic faults such as myopia and high blood pressure are fixed. The bumps along the spine as well as the nipples fade. Finally, white stripes and ridges start growing over their bodies. Ulam reports that the cells seem to sing.
Through infection, conversion and assimilation of humans and other organisms the cells eventually aggregate most of the biosphere of North America into a region seven thousand kilometres wide. This civilization, which incorporates both the evolved noocytes and recently-assimilated conventional humans, is eventually forced to abandon the normal plane of existence in favor of one in which thought does not require a physical substrate. - from Wikipedia