Researchers at various institutions are experimenting with a controversial practice which involves potentially growing human organs inside of animals; while there are ethical concerns, the intention of the science is to increase the supply of human organs for transplant purposes.

Since there aren't enough human organs available for transplantation, a controversial practice involving what is called human-animal chimeras has emerged.
It is the attempt to grow human tissue, such as livers and hearts, inside animals like sheep and pigs with the goal of later removing the organs and implanting them into needy recipients. 
The proce