"Organ humanizing" is the process of injecting your stem cells into an animal foetus, so that when it is born, its organs' cells will be similar enough to your own that they can be used for spare parts.
The human cells must be injected around halfway through gestation – before the fetus's immune system has learned the difference between its own and foreign cells, so that the animal does not reject them, but after the body plan has formed.
That ensures that the resulting animals look like normal sheep rather than strange hybrids like the "geep", created by fusing the embryos of a sheep and goat.
