A xenograft is a type of transplant where tissue or organs are taken from one species and implanted into another. This procedure is often used in medical research and treatments, particularly when human tissues are not available. Common sources for xenografts include animals like pigs or cows, which can provide organs or skin for transplantation. Xenografts are important in the field of regenerative medicine and organ transplantation, as they can help address the shortage of human donor organs. However, there are challenges, such as the risk of rejection by the recipient's immune system and the potential for disease transmission from the donor species.