It's a question children are asked a lot. They often have ambitious plans to be doctors, astronauts, footballers or teachers.
However, for the hundreds of children with blood cancer or a blood disorder who are in need of a blood stem cell transplant, these dreams are put on hold while they search for a matching donor.
Josie loves dressing up and playing with her first aid kit; she dreams of being a doctor herself one day.
At the moment, daily life is a challenge for her. Her rare and serious congenital disease means that Josie spends much of her time in a real hospital. The stream of specialist doctors seems endless; it is little wonder that she wants to be just like them when she grows up.
The only way for Josie to have a good quality of life is a blood stem cell transplant. Her condition is so rare that nothing short of a perfect match will do. There is currently no one on the register who is a suitable match.
It costs £40 to register a potential lifesaver to the stem cell register. You could help by funding a potential lifesaver for Josie or one of the 600 other children just like her who are diagnosed with blood cancer or a blood disorder every year.