In November, for example, a company in California cancelled what had been the first trial of human embryonic stem cells, in those with spinal injuries.
Unfortunately, it's the stem cells from embryos that have shown the biggest potential, for generating both a range of tissues and a ton of controversy.
Dr Schwartz and his team coaxed embryonic stem cells to become retinal pigment epithelium tissue which supports the rod and cone cells that actually respond to light
Embryonic stem cell has the ability to differentiate into any necessary type of body cells, while adult stem cell has limited differentiation of cells specific only to its tissue origin.