What are stem cell and why are the so important? Embryonic stem cell research is believed to hold the key for better treatment, and possible cures for some serious illness. Stem cell are primitive cells and they have the ability to change into many different types of cells . There are over 300 district types of cells in the human body, but stem cells are the only types that can be grown into other kinds of cells . This is very useful for scientists and doctors. They hope to grow stem cells to regrow damaged tissue or treat injuries . Using mice, scientists have successfully cored Parkinson's disease, damaged nerve tissue, and eve diabetes. Now the challenge is to do the same with humans .