Chimeras in the biological and medical sense are organisms that consist of cells or tissues of different individuals and yet form closed and viable (not necessarily reproductive) organisms. They can be located within a species or between species and can be both plants and animals. There are natural (blood chimeras in mammals) and artificial mixed organisms (grafting in plants, animal-human embryos). Cyborgs are not chimeras in this sense. Nevertheless, research in this field might also be relevant for them, in particular for inverted or reversed cyborgs, for example robots in which an animal or human brain or organ is implanted. Animal-human chimeras for the production of human organs are regarded as unproblematic by many ethicists. According to a comment by Oliver Bendel, this is astonishing, since findings from animal ethics and veterinary medicine and in particular suffering and death of non-human living beings are ignored.