Stem cells
...ed stem cells, or "blank" cells. Because they are blank, they will become whatever type of surrounding cells you place around them. Scientists have been doing tests to small animals like rats which have diseases like macular degeneration. They were able to remove the damaged cells, replacing them with stem cells and those stem cells then became the missing muscle tissue, which cured the rat of the disease. So theoretically, if they were able to do this with humans, they would be able to cure such diseases such as Parkinson's and Alzheimer's disease, multiple sclerosis, diabetes and even some types of cancer. But the best source of stem cells is human fetal tissue, and harvesting the stem cells destroys the embryo, which many see as morally problematic. There isn't just one type of stem cell to extract, there are a few such as embryo stem cells, fetal stem cells, and adult stem cells. This of course raises the question "why don't scientists just extract adult stem cells" but the problem is that adult stem cells are much less potent compared to the embryo cells. In other words the older the human gets, the less potent the stem cells become. The first step in human development is when the newly fertilized egg begins to divide producing a group of stem cells called an embryo. These early stem cells are totipotent which means they can become any type of cell they want. Toti is latin for "total" so think of the cell as having total potential. After the eighth week of development, the embryo is considered a fetus ...