In cell culture, stem cells have the ability of dividing indefinitely, as well as differentiating into numerous cell types. They differ in potency: unipotent stem cells develop into one specialised type of cells, multipotent ones are able to develop into multiple types of cells and tissues, pluripotent ones into the majority or all cell types of a mature organism, totipotent cells into all cell types of a mature organism, as well as specialised tissues that support embrional development. This paper presents a brief overview of stem cell, cultivation techniques and possible areas of clinical applications and the scientific research, as well as ethical controversies related to sources and further application of stem cells. Although stem cells have been used in the treatment of leukemia and in treatments of skin burns, by using transplantation, for over thirty years now, in the recent history of medicine this topic became the cause of many controversies. Nowadays, stem cells are mostly derived from embryos made by artificial insemination, but embryos made by transplantation of the nucleus of the donor's body cells into an unfertilized egg cell (therapeutic cloning) could be used as well. Since the embryo is destroyed during the act of acquiring EM cells, scientists turn to other types of stem cells, such as adult stem cells or stem cells which can be derived from the blood of umbillical cords. A lot of effort and resources is put into researching ways of creating stem cells from differentiated cells (like skin cells) without the usage of egg cells. In any case, the quest for a way to guide stem cells into differentiated cells that will be functional after transplantation into a living organism is in full throtle. This quest gives hope to those suffering from diabetes, Alzheimer's and Parkinson's disease, cardiovascular diseases, carcinomas, rheumatoid arthritis etc.