First technicians extract embryonic or adult stem cells from a pig, cow, chicken or any other animal. Then they grow cells in bioreactors. Then technicians instruct the cells to transform themselves into muscle cells (instead of e.g. bone or brain cells). In the final stage trains the muscles to grow. The muscle cells brought to a greater density at this time. One difficulty is that producing stem cell lines grow at a stretch and suddenly decide they want to be something else. Another challenge is for the security to ensure that when stem cells are instructed to form muscle tissue the vast majority does.