A Klein bottle can't hold any liquid because it doesn't have an inside. How do you construct this strange thing and why would you want to?
Why doing maths is like being Lewis Carroll's Red Queen and how to keep going beyond the formidable age of 84.
Maryam Mirzakhani is being honoured for her "rare combination of superb technical ability, bold ambition, far-reaching vision, and deep curiosity".
The paths of billiard balls on a table can be long and complicated. To understand them mathematicians use a beautiful trick, turning tables into surfaces.
Topology considers two objects to be the same as long as you can morph one into the other without breaking it. But how do you work with such a slippery concept? One useful tool is what's called the fundamental group of a shape.