Magnify his best traits.
In "The Brain Bowl Incubation" (Episode 8, Season 10), Amy speculated that Sheldon would enjoy assisting in her fun DNA experiment, but she had no idea just how invested he'd become.
Sheldon was floored when he saw how well his skin cells bonded together with Amy's under a high-tech German microscope; he was so floored, in fact, that he appeared to temporarily lose all his common sense.
Determined to create the perfect organism, Sheldon attempted to break the couple's annual coitus agreement and get busy with Amy right then and there in the lab!
It turns out, the best way to Sheldon's heart is through his ego—and possibly his genomes.