The tightest knotted structure is 2.5 nanometres per crossing, achieved by David Leigh, Jonathan J. Danon, Alexander J. Stephens (all UK), Steffen L. Woltering (Germany), Jean-Francois Lemonnier (France), Anneke Krüger (South Africa) and Iñigo J. Vitorica-Yrezabal (Spain), in University of Manchester, Manchester, United Kingdom, on 12 January 2017.