Phlox's creation in 2153 of Sim, a mimetic simbiot grown from Trip Tucker's genetic material so that neural tissue could be transplanted to save the comatose engineer.
The creation of Sim is the subject of the Enterprise episode Similitude. During the mission in the Delphic Expanse an accident in engineering leaves Trip Tucker in a coma. Phlox proposes injecting Tucker's DNA into a Lyssarian desert larva, which will grow into a copy of him with a lifespan of about fifteen days.
Archer approves, since the mission cannot spare its engineer. Sim grows from infant to adult within days and, unexpectedly, carries Tucker's memories. He helps free the ship from a cloud of particles clinging to its hull and tells T'Pol of his feelings for her.
It emerges that the transplant will kill him. Sim thinks of fleeing in a shuttlepod and of an untested enzyme that might lengthen his life, but in the end goes willingly. The crew give him a funeral with full honours.