"Fertile" intestine nuclei.

Gurdon and Uehlinger replaced the cell nucleus of frog ova with frog intestinal nuclei to generate tadpoles, some of which became fertile adult male and female frogs.

In 2012 the Nobel Prize in Physiology or Medicine was awarded jointly to Sir John B. Gurdon and Shinya Yamanaka "for the discovery that mature cells can be reprogrammed to become pluripotent."  See also No. 256.12.

(Thanks to Juan Weiss for this reference and its interpretation.)