Chimeras that originate from distinct fertilised eggs fused together are called dispermic chimeras. When, on the other hand, the genetically distinct cell types originate from the same zygote, the organism is called a mosaic.
Dispermic chimaeras are formed from at least two fertilized eggs or early embryos fused together. Each population of cells keeps its own phenotype and the resulting organism is a mixture of the two phenotypes.
Microchimerism is a form of chimerism in which a host harbors a small set of genetically distinct cells. This often happens with blood transfusion or transplants, but also during pregnancy due to the two-way cell trafficking between the mother and the foetus.
Recently, epigenetic chimeras have been discovered in mouse models.
Chimaera (genetics) Facts for Kids. Kiddle Encyclopedia.