We've all heard of origami. It's all about making paper birds and pretty boxes, and is really just a game invented by Japanese kids, right? Prepare to be surprised as Liz Newton takes you on a journey of origami, maths and science.

One million dollars is waiting to be won by anyone who can solve one of the grand mathematical challenges of the 21st century. In the second of two articles, Chris Budd looks at the well-posedness of the Navier-Stokes equations.