This could eventually end the problem of the world shortage of donor organs for transplants:
http://www.newscientist.com/article/mg20227114.600-hybrid-hearts-could-solve-transplant-shortage.html
For example, it has been shown that you can use detergent to wash away cells in a pig’s heart so that all is left is a ‘scaffold’ of collagen and then this ‘scaffold’ can be seeded with human stem cells (possibly from the patient to avoid the problem of organ rejection) and the stem cells differentiate into the various kinds of heart cells on this scaffold creating a fully functional heart ready for transplant.