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?

Our image of the week shows one of our favourite topological shapes.

Lucinda Mathews visualises tricky surfaces

Conversations across science and art

Mathematics illustrates the forefront of visualising science

In the first of a new series 'Imaging Maths', Plus takes an illustrated tour of an extraordinary geometric construction: the Klein bottle.

Is the Universe finite, with an edge, or infinite, with no edges? Or is it even stranger: finite but with no edges? It sounds far-fetched but the mathematical theory of topology makes it possible, and nobody yet knows the truth. Janna Levin tells us more.