4 facts you never knew about the heart
On 3 May 1968, one person's heart made history when it was used in the UK's very first heart transplant.
The operation was carried out by a team of 18 doctors and nurses at the National Heart Hospital in Marylebone in London.
To mark the occasion, we're taking a look at just how amazing our hearts really are.
Did you know any of these amazing facts before?