If you want to climb vertical walls you need very large feet — or be as small as a gecko.

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?

How to keep warm and safe
Mathematicians quest for the perfect poppyseed bagel!
In the first of a new series 'Imaging Maths', Plus takes an illustrated tour of an extraordinary geometric construction: the Klein bottle.
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