Chimera is a composite organism, consisting of cells derived from more than one embryo. The first experimental chimera was produced in 1961 and until today, chimeric animals have been widely used in mammalian experimental embryology. Numerous aggregation and injection techniques have been used to produce chimeras. Although most experimental chimeras were made of murine embryos, chimeric animals have been also produced in such species as: rat, hamster, deer mouse, rabbit, pig, sheep and in cattle. Some successful attempts to produce interspecific chimeras have been also made. Pigmentation is still widely used as a marker of chimerism, but new transgenic markers are now available. New methods emplying chimeric technique, like blastocyst complementation assay and lethal phenotypes rescue, provide new insights into developmental genetics. Nowadays, chimeric embryos are also likely to play a major role in the production of transgenic animals with the help of chimeric cloning technique.