Cloning is the process of making copies of a specific piece of DNA, usually a gene. When geneticists speak of cloning, they may not mean the process of making genetically identical copies of an entire organism, but of making a copy of a small piece of DNA. To date, the highest species to be cloned are non-human primates. There are currently strict NIH regulations against the cloning of humans; few groups support the cloning of entire humans, though the cloning of select organisms in host animals (e.g. growing replacement human hearts in pigs) is a long term goal of the scientific community. Recently, proof-of-concept experiments growing cloned rat organs in mice and via versa have demonstrated the feasibility of one day growing cloned human organs in host animals.