Babies made from two women and one man have been approved by the UK's fertility regulator.
The historic and controversial move is to prevent children being born with deadly genetic diseases.
Doctors in Newcastle - who developed the advanced form of IVF - are expected to be the first to offer the procedure and have already appealed for donor eggs.
The first such child could be born, at the earliest, by the end of 2017.
Some families have lost multiple children to incurable mitochondrial diseases, which can leave people with insufficient energy to keep their heart beating.