Doctor Bathkin of Andros III was the first to come up with the answer to solving the puzzle of death: by keeping the cells of the body energized -- keeping them in the game by teaching them new mitochondrial tricks.
Dr. Bathkin later died in a shuttlecraft accident in 2359 before he could ever finish his work.
His work would eventually be completed in 2373 by Dr. Elias Giger in what became known as the cellular regeneration and entertainment chamber. (DS9:"In the Cards")