These types of procedures involve genetically editing organisms to understand the function of their genes. For example, using Cre-recombinase, an enzyme which makes specific cuts in the genome, researchers were able to knockout the expression of Sp8, a gene hypothesized to be essential for face development. In the resulting mouse model, it was observed that facial development was significantly impaired, yet a tongue and a mandible were present (see image).[1] Transgenic animal models is just one way in which researchers are attempting to understand craniofacial abnormalities.