A UK-wide vote is taking place to decide which world problem should be the focus of a global science challenge.
is offering £10 million to whoever can solve the issue that's chosen by the public.
Voters are deciding between six problems.
In this report, Ayshah looks at dementia, a common condition that affects the brain.
There are about 800,000 people in the UK with dementia, which can cause problems with things like memory, language and emotions.
How can we help people with dementia live independently for longer?