What is cystic fibrosis?
Cystic fibrosis is a condition which is very bad for people who have it. It mainly affects children and younger people.
How serious is it?
At the moment the average person with the condition dies in their 30s.
It can make it very difficult to breathe. It leads to the clogging up of the lungs, and other organs including the pancreas and intestines, with thick, sticky liquid called mucus.
What happens to people who have it?
Because it damages lungs, people with cystic fibrosis often have coughs and chest infections.
Some of the organs it damages are very important in digesting food. That means people with it are often smaller and not as strong as they should be.
How do you get it?
Cystic fibrosis isn't caught from another person. You either have it or you don't.
It is inherited, which means it is passed on by adults when they have children, although the parents of kids with it don't have the disease themselves.
According to the National Health Service (NHS), cystic fibrosis is the most common inherited disease in the country, with one in every 2,500 babies born with it.
Can it be treated by doctors?
There is no cure for the condition, although people who have it now live longer than they used to.
Scientists hope that by studying the way genes work may one day help them come up with a cure.
It is really important for children who have it to do as much exercise as possible. It helps keeps their lungs clear of the mucus, and makes them stronger and healthier.
Some patients even have a lung transplant.