Regulators in the UK have given scientists the green light to create human-animal embryos for research.
The Human Fertilisation and Embryology Authority granted permission after a consultation showed the public were "at ease" with the idea.
Experts said it was vital for research into life-threatening diseases.
Two centres, King's College London and Newcastle University, will now be able to begin their work under one-year research licences.
Any other centres wishing to do similar work will have to apply to the HFEA for permission, which will make a decision on a case-by-case basis.
Scientists want to create hybrid embryos by merging human cells with animal eggs in a bid to extract stem cells. The embryos would then be destroyed within 14 days.
The cells form the basic building blocks of the body and have the potential to become any tissue, making them essential for research.
Dr Armstrong said: "Now that we have the licence we can start work as soon as possible.
clipped from: news.bbc.co.uk