The filter is the most finely constructed example of the mathematician`s `Turing structures` yet, and their first practical application, say researchers. [These 3D structures are quite extraordinary," says Patrick Müller, a systems biologist at the Friedrich Miescher Laboratory in Tübingen, Germany. The filter`s tubular strands, just tens of nanometres in diameter, would be impossible to produce by other methods, such as 3D printing, he says. The work is published on 3 May in Science1.