Topology has played a central role in modern physics. New phases of matter and phase transitions (1, 2), as well as electronic band theory (3), are understood in terms of topological concepts. On page 1449 of this issue, Tai and Smalyukh (4) harness topology to create a fundamentally new type of crystal, built with knots tied in a chiral fluid (see the figure). They used a liquid crystal doped with a chiral molecule, which caused all of the molecules to rotate like a corkscrew along a preferred direction, the helical axis. Using electric fields, they created vortex lines in the helical axis and tied them into knots that act like “atoms” but on the micrometer scale. Different knotted particles were created by careful illumination with laser tweezers, and their interactions were tuned so that they spontaneously assembled into two- or three-dimensional lattices.

Gareth Alexander's paper appears in Science, Vol. 365, Issue 6460, pp. 1377

DOI: 10.1126/science.aaz0479

The LHCb collaboration has, this week, published long-awaited results on matter-antimatter asymmetries in B+ → π+π+π− decays, explaining the curious variation of the asymmetry across the phase space.

On 8 September, David Armstrong of the Astronomy and Astrophysics group appeared on the iconic BBC astronomy show "The Sky at Night" to discuss the hunt for exoplanets with host Maggie Aderin-Pocock.

The episode is available on BBC iPlayer until 12 October.