Stem cell culture. Scientist examining a petri dish used to culture human embryonic stem cells (HESCs). The HESCs are held within the drops of liquid. This is a hanging drop culture used when inducing the cells to differentiate. HESCs are pluripotent, they are able to differentiate into any of the 200 cell types in the human body. The type of cell they mature into depends upon the biochemical signals received by the immature cells. HESCs are a potential source of cells to repair damaged tissue in diseases such as Parkinson's and insulin-dependent diabetes, and after heart attacks. However, use of HESCs is controversial as it requires the destruction of an embryo.