So how does the miracle machine work? First, it’s heated to roughly 98.6 degrees Fahrenheit, the temperature of the human body, according to the German news outlet The Local. Next, robotic hands meticulously extract cells from foreskins donated to the project, all samples of which must come from boys age four-and-under.

“The older skin is, the worse the cells function,” Andreas Traube, an engineer at the institute.