Human cells are diploid (contain a double set of chromosomes). The diploid genome is complex and therefore limits genetic research approaches in biomedical models. To overcome this problem experimental generation of haploid stem cells has been done in animal models. haploid cells are easier for genetic manipulations, such as knock-in and knock-out of genes, and therefore should make a better experimental model. The investigators aim at generating haploid stem cells from human haploid germ cells.