Stem cells are cells that can be divided or self-replicate for a long period of time, in most cases throughout the life of the organism. Under controlled conditions, stem cells can replicate into different types of cells that comprise the cellular structure of an organism. This implies that stems cells have the ability to grow to mature cells that have defined characteristics and functions like heart cells, nerve cells, skin cells, or others. It is because of this ability to replicate to specialized cells that they have become important in the field of medicine. They have been proposed as possible cures for a wide range of health conditions that have not been cured through conventional medicine. Stem cells have greater potential to revolutionize the field medicine. However, stem cells have been criticized on social, religious, and scientific basis.