The cover picture depicts the process of producing mouse embryos from cultured medulloblastoma cells by nuclear transfer into oocytes. The upper left panel shows a sagittal section through a Ptc1^+/- mouse brain containing a spontaneously arising medulloblastoma in the posterior cerebellum (highlighted in light blue). The upper right panel shows cultured medulloblastoma cells derived from such a tumor immuno-stained for both GFAP (red) and neurofilament (green). The central panel shows the enucleation of a mouse oocyte prior to transfer of medulloblastoma nuclei. The lower left panel shows a cloned pre-implantation blastocyst and the lower right panel a cloned E7.5 post-implantation embryo generated from medulloblastoma nuclei. For more information, please see the article by Li et al., on p. 2733 of this issue. Cover image montage design by Dr. Gopal Murti and Ken Barnes of the Scientific Imaging Center at St. Jude Children's Research Hospital, Memphis, TN.