Mathematicians have made a crochet model of chaos - and are challenging anyone else to repeat the effort.
Dr Hinke Osinga and Professor Bernd Krauskopf, of Bristol University's engineering mathematics department, used 25,511 crochet stitches to represent the Lorenz equations.
The equations describe the nature of chaotic systems - such as the weather or a turbulent river.
The academics are offering a bottle of champagne to anyone who cares to follow the pattern published in the journal Mathematics Intelligencer.
The idea for the Lorenz manifold model came to the couple during the Christmas break two years ago.
Dr Osinga, who learnt to crochet when she was seven, was relaxing by crocheting some hexagonal lace motifs.
Prof Krauskopf asked her: "Why don't you crochet something useful?"
Eighty-five hours of work and some supporting steel wire later, they had something almost a metre across which looks not unlike a big Christmas decoration - which is what they are using it as.
Dr Osinga, said: "Imagine a leaf floating in a turbulent river and consider how it passes either to the left or to the right around a rock somewhere downstream.
"Those special leaves that end up clinging to the rock must have followed a very unique path in the water.
"Each stitch in the crochet pattern represents a single point - a leaf - that ends up at the rock."
The more serious side to the work was developing a computer model to describe complex surfaces.