Researchers published in Cell this week the successful implantation of pig embryos with human pluripontent stem cells. Within the paper researchers also investigated the capabilities of grafting other PSCs (human and mouse) into different mammalian embryos. While not all were successful, the findings reported here may make it possible to identifying some of the variables (timing, environment, cell types, species type, etc) to develop chimeric tissues, organs, or maybe even species (probably far far away). Can you think of any specific species specific attribute which could be very useful in a chimeric? What about a plant/mammalian chimeric? What would be going too far in making a chimeric?