Nature: More than a century after the idea was first floated, physicists have finally figured out how to tie water in knots in the laboratory. Creating a knot in a fluid bears little resemblance to tying a knot in a shoelace. The entire three-dimensional (3D) volume of a fluid within a confined region, such as a vortex, must be twisted. Physicists Dustin Kleckner and William Irvine have now created a knotted vortex using a miniature version of an aeroplane wing built with a 3D printer. The researchers submerged their tiny wings in a tank of water and gave it a sudden acceleration to create a knotted structure. This research was conducted at the Irvine Lab at University of Chicago.