A press report in the Daily Mail broke the news that the world's first genetically manipulated babies had been born in the USA. Infertility had been diagnosed as due to a defect in the mitochondrial DNA. To rectify this, mitochondria from a donor was introduced into the defective eggs. This meant that the children born had nuclear DNA from their parents but mitochondrial DNA from the donor. Effectively there were three people contributing to the DNA of the offspring.
You can read more about it on the BBC news site here.