A xenograft is a type of transplant where tissue or organs are taken from one species and implanted into another species. This procedure is often used in medical research and treatments, particularly in cases where human tissues are needed for study or when human organs are not available for transplantation. Common sources for xenografts include animals like pigs or cows, which are chosen for their physiological similarities to humans. While xenografts can help advance medical science, they also raise ethical concerns and potential risks, such as the transmission of diseases from animals to humans.