Experiments on twin children in concentration camps were created to show the similarities and differences in the genetics of twins, as well as to see if the human body can be unnaturally manipulated. The central leader of the experiments was Josef Mengele, who from 1943 to 1944 performed experiments on nearly 1,500 sets of imprisoned twins at Auschwitz. About 200 people survived these studies.[4] The twins were arranged by age and sex and kept in barracks between experiments, which ranged from injection of different dyes into the eyes of twins to see whether it would change their color to sewing twins together in attempts to create conjoined twins.[5][6]