To become a bone marrow donor, you have to be a blood a donor first, so that your blood can be checked and you must be aged between 18 and 49 years old.
You can join when you next give blood, or at the same time as your first donation. They will then check that there is no medical reason preventing you from being both a blood donor and a stem cell donor.
At the time of your blood donation they will take an extra blood sample, so that they can identify your tissue type for the registry from your DNA - the genetic material our bodies are made up from.
More top news
Since starting school Anthony Mousiou has been internally excluded - pulled out of lessons to study alone - over the length of his hair.
When you're trying to concentrate even the slightest sound can be a distraction.
The court heard how Roland McKoy killed his 22-month-old daughter Jahzara out of 'spite and resentment'.