1. Tyson Biology 1 Stem Cells Stem cells are cells that are unspecialized and work as a repair system for the internal body. When they divide, they have the choice to stay a stem cell or become another type of cell. They are mostly used to help stop diseases. They can form to become almost any type of cell they are needed to be. There are 2 main types of stem cells: embryonic and adult. Embryonic stem cells come from 4-5 day old embryos that have stem cells that can be extracted. They last long, but are not nearly as reliable as adult stem cells. Adult stem cells are undifferentiated cells that can be found in tissue and organs that can renew itself. Their main purpose is to repair damaged cells and tissue. They are very reliable, but they do not last as long as the embryonic stem cells. They were banned from government funding in the USA for the past 8 years for the reason that embryonic stem cell require the abortion of a 4-5 day old embryo. The ban was recently released. In my opinion.