10 Darkest Star Trek: Enterprise Moments

In the episode Similitude, Trip was critically injured by an explosion in engineering while saving the ship from a warp core breach. Dr. Phlox then determined that the only way to save him was by harvesting neural tissue from a clone of Trip grown in his lab.

This clone, which they named Sim, grew at an accelerated rate, going from a child to an adult in only a few days. Somehow, Sim retained Trip's memories, and eventually got to work helping the crew solve problems on the ship, just as Trip did. They originally believed that Sim could survive the procedure to save Trip, but they eventually learned that was not the case. Sim pleaded with Archer and Phlox to slow his ageing and allow him to replace Trip, but Archer insisted that they were not the same.

Sim considered escaping, but chose to stay and sacrifice his life for Trip's to ensure that the Xindi mission was completed. Sim remembered Trip's sister Elizabeth who died in the Xindi attack, and was willing to do anything to make sure what happened to her didn't happen to anyone else. It's worth noting though that Archer was perfectly willing to force Sim to comply.