The UK's first ever 'three person baby' has been born and they're one of only a handful of children around the world who share the DNA of three people.
The vast majority of the child's DNA comes from their parents, but around 0.1 percent is from a donor and while it might not seem like much, the difference could be life changing for the child.
With just 0.1 percent of DNA from a third person, a baby might avoid being born with mitochondrial diseases which are incurable and can be fatal within days or even hours of birth.
You might have heard that mitochondria is the powerhouse of the cell - almost every cell in your body has mitochondria which convert food into energy.
A person born with defective mitochondria will have cells that don't get fuelled properly, which can lead to death or debilitating illnesses as muscles are undersupplied and vital organs don't get the energy they need.
Doctors are being very secretive about the groundbreaking procedure as the Human Fertilisation and Embryology Authority (HFEA) wants to maintain patient confidentiality and provided no further details about the births.
The 'three person baby' is something scientists are hoping will provide a way around the risk of incurable mitochondrial diseases.
Mitochondria are passed down via the mother and by adding mitochondria from a healthy donor egg during IVF it is hoped that this could successfully head off any health issues.
With the 'three person baby' some DNA from the third person is going to end up in the child, though it only affects their mitochondria and doesn't have an impact on things like appearance.
The UK is not the first country to try this, as in 2016 a US doctor announced that the world's first baby born with mitochondrial donation treatment had been born, though the process did originate in Newcastle.
The mother of the world's first 'three person baby' was a Jordanian woman who had suffered four miscarriages and lost two other children before the age of eight.
She was found to carry mitochondrial mutations which caused a fatal condition called Leigh Syndrome.
Laws were introduced in 2015 to allow the process to go ahead in the UK, though it would be several years before the first baby was born with the procedure.