Stem cells have the ability to develop into a variety of cell types (NIH, 2016). They start as a type of undifferentiated cells that have the capability to then differentiate into much more specialised cells,this can include nerve, muscle or bone cells (MNT Editorial Team, 2017)(Stem Cell Network, 2013). Stem cells have two main characteristics that makes them different from others cells (NIH, 2016). Firstly, they are unspecialised cells that can renew themselves through the process of cell division (NIH, 2016). Secondly, in certain scientific conditions the cells can become tissues or other specific cell types (NIH, 2016). In certain parts of the body it is common for stem cells to be present and dividing in order to repair any damaged tissue, for example within bone marrow (NIH, 2016). In other areas of the body, however, stem cells will only begin to divide under specific conditions (NIH, 2016). As stem cells can be a continuous source of new tissues, it is thought that it could transform modern medicine to create treatments (Stem Cell Network, 2013). Stem cell potency is the cells ability to differentiate into a variety of cell types (Fullick, Locke and Bircher, 2015). The greater the potency then the more cell types it can differentiate into (Fullick, Locke and Bircher, 2015). Totipotent stem cells can differentiate into any cell type, examples of totipotent cells include fertilised egg, zygote or 8 or 16 cells (Fullick, Locke and Bircher, 2015). These cells will eventually produce an organism but and can also differentiate into embryonic tissues such as amnion and umbilical (Fullick, Locke and Bircher, 2015). Pluripotent cells can differentiate into cell types but will not produce a whole organism (Boyle and Senior, 2008). They will develop into different tissue types and are present in early embryos (Fullick, Locke and Bircher, 2015). Multipotent cells can produce a variety of cells for a certain tissue type (Fullick, Locke and Bircher, 2015). The first main type of stem cells are adult stem cells which can be found in areas of the body such as bone marrow, fat and peripheral blood (Riordan, 2017). These are the stem cells that will exist after embryonic development (MNT Editorial Team, 2017). Just because stem cells are present does not mean they will always be dividing and many adult will be in a nondividing state until triggered by an illness or disease (MNT Editorial Team, 2017). Stem cells in adults have the ability to regenerate cell types from the organ they came from, for example in the liver where stem cells are found, tissue can be regenerated sometimes enough to repair damage (MHT Editorial Team, 2017). The second type of stem cells is embryonic stem cells, these cells are present in embryos at around four or five days old (MNT Editorial Team, 2017). Often embryonic stem cells come from extra embryos created during the process of IVF where the embryo is in the blastocyst phase of development (MHT Editorial Team, 2017). Adult stem cells and embryonic stem cells have similarities, for example they can both differentiate into a variety of cell types, but sometimes embryonic stem cells are preferred as they can be relatively easy to grow in culture and in some cases more easy to obtain as it can be difficult to collect adult stem cells due to their rarity and isolation of the cells can create difficulties (NIH, 2016). Although, it is believed that adult stem cells may have a less likely chance of rejection (NIH, 2016). To back this point up, some initial research done by Stanford University of Medicine on mice has shown a very highly likely chance of embryonic stem cell rejection (Swaminathan, 2008). The use of both adult stem cells and in particular embryonic stem cells has drawn controversy from many (Phillips, 2017). When stem cell research began in 1998, a conversion started into the ethical issues surrounding stem cells with a mixed response (Genetic Science Learning Center, 2014). One of the debates in favour of stem cell research was the medical potential in areas of medicine that had yet to be properly researched (Phillips, 2017). Stem cells have the ability to be treatments and even cures for cancers, Type 1 diabetes, spinal cord damage, Alzheimer’s, Multiple Sclerosis, Parkinson’s and a variety of other genetic illnesses (Phillips, 2017). This medical potential can often outweigh the ethical issues as using embryonic stem cells can alleviate the suffering of many (Phillips, 2017). However, there have been many discussions about using embryos in research as the embryo would be destroyed (Genetic Science Learning Center, 2014). Therefore, discussions around when life begins have been raised as if life begins at fertilisation then using embryos in research would effectively be ending a life (Genetic Science Learning Center, 2014). New developments into adult stem cells and alternative options have made it less ethically challenging to obtain and research stem cells, this can help broaden the medical research field by allowing a greater opportunity to study stem cells without the ethical and controversial risks (Phillips, 2017). Stem cells can be used in medical research quite heavily to treat and even possibly cure a vast range of diseases and injuries (California Institute for Regenerative Medicine, 2015). Stem cells can be used to treat and repair damaged tissues, particularly were the extent of cellular damage is too great that transplant is unlikely to succeed (Sapolsky, n.d.). As long as blood is still being supplied to the damaged area, in theory stem cells can be used (Sapolsky, n.d.). An example of this process is stem cell research into Type 1 diabetes were stem cells are differentiated using culture to form insulin producing cells (NIH, 2016).