Crystal clear: After two decades of controversy the elusive skew-boat conformation of L-iduronic acid (see picture) was finally ascertained at atomic resolution in a synthetic, substituted disaccharide. This highly flexible compound crystallizes in two dimorphs. This rare case of dimorphism in oligosaccharides is all the more remarkable in that the 2S O conformation crystallizes in both forms. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.