An ethics committee at the Royal Free Hospital has given the go-ahead for the world's first full face transplant. But what does this decision mean?
What has been decided?
Mr Peter Butler, a surgeon at the Royal Free Hospital, London, approached the ethics committee at his hospital to seek permission to carry out the world's first face transplant.
Gaining approval from an ethics panel is essential for scientists wishing to carry out any research involving humans.
The panel has been considering whether the surgery and drugs used afterwards to prevent rejection of the tissue are safe, and whether the patient would be able to cope with any psychological impacts of such a procedure.
By giving Mr Butler the go-ahead, they have deemed the operation to be safe and ethical.
Does this mean something will happen straight away?
Mr Butler said he expected an operation to take place within "a year".
He has identified about 30 possible patients who will be assessed to see if they fit the selection criteria.
His team will then choose the final four patients, from the UK or Ireland, who will receive face transplants.
What will happen during the operation?
During the surgery, one team will remove skin grafts and any other reconstructive surgery from the face of the patient.
A second team will detach the face from the donor, removing the skin, underlying fat and eight different blood vessels, four arteries and four veins.
The face will then be kept on ice for transport to the patient, and stitched into place in a delicate procedure expected to take 14 hours.
What has happened so far?
Last November, Frenchwoman Isabelle Dinoire was the first person to receive a partial face transplant after she was mauled by her dog.
A team of medics, from Amiens in France, transplanted a section of a nose, lips and chin from a donor who was brain dead.
In April, Li Guoxing, 30, underwent the 14-hour operation in Xijing hospital, central China, to receive a new upper lip, cheek and nose.
Are their risks involved with the procedure?
Medically, the procedure does carry risk.
In the short term, clots could form in the donated tissue, and, in the longer term, the immunosuppressants may fail.
The risks of rejection are relatively high. Senior surgeons estimate one in 10 patients could suffer rejection within six weeks. Up to half could suffer chronic rejection after a year.
Taking immunosuppressants also increase a person's cancer risk, so anyone who considering a face transplant would have to decide whether the benefits outweighed the risks.
What are the ethical arguments against face transplants?
The psychological effects, both on the patient and on the donor's family, are a major concern.
There are doubts that families would consent to have the face of their loved one removed and transplanted onto someone else.
If they did give permission, how would these families react if they were to meet or see the patient?
And the recipient would have to come to terms with the fact that they do not look the way they did before.
They would also have to be comfortable wearing someone else's face. This cannot be taken for granted.
The man who received the world's first hand transplant asked for it to be removed, partly because he didn't like having somebody else's hand.
What would the donor look like?
They would not have the same skeleton and facial shape as the donor, so they would not look like them. But neither would they look as they did before.
Computer simulations have shown that donor families would not recognise the face on a recipient.
Step one: Skin and muscle tissue, eight different blood vessels, four arteries and four veins cut away from donor's face
Step two: Blood vessels and nerves from face section connected to recipient using microvascular surgery