As reported by [wired]:

Replacement human organs are hard to come by, generally the only way to land your hands on one is if someone donates them upon death, assuming their not hamburger. To that end, medical scientists have been working hard on things like [3D printing human organs], or [synthetic organs]. Another way however is through genetic engineering...

How it works is they select an embryo from a target host, such as a pig, then use CRISPR to knock out the genes for the target organ they want to gestate, for example lets say a heart. When the embryo is still in development in the early stages, they inject human stem cells from the target recipient into the embryo, so as it grows and matures, it will have a pig body with a human heart, ready to transplant into the patient. The ethical reasoning behind this is that we slaughter pigs and similar farm animals for food anyway, why not organs too, and solve the chronic shortage of available organs? However, there are certain... complications.

You see, human cells transplanted into the host don't exactly stay still, they migrate throughout the body, including to the brain, creating the potential for these human host animals to possess human intelligence. The fantasy films of The Secret Of NIMH, or Animal Farm may not be so fictional in the near future. Trials are underway for [Human Mouse] hybrids in Japan, with restrictions that their brains not possess more than 30% human cells, lest they create "humanized" animals.

For the Planet Of The Apes types, other work has surfaced with scientists creating [Human Monkey hybrids in China, irritating authorities after the recent attempt to genetically engineer two human children. Suffice it to say, incidents like this are likely to increase given the ready access to genetic engineering technology, with the world on a collision course with our concept of what it means to be human.