AbstractThe cover picture is a composite design depicting the variety in NHC complex chemistry. Like pieces in a puzzle, all details contribute to our growing knowledge of these compounds. The first puzzle piece in the bottom left corner represents the carbene precursors, essential in all synthesis design (C. W. Bielawski et al.; p. 1729f f). The background reflects the importance of these complexes, here in the homogeneous catalytic chemistry of gaseous molecules (C. M. Crudden et al.; p. 1746 ff), while the diverse structural types are highlighted by the zwitterionic “crabenes” mid right (L. Delaude; p. 1681 ff). Related aspects such as the physical chemistry or biological relevance are not forgotten: the sketch of the buried volume of an NHC ligand symbolizes the former (L. Cavallo et al.; p. 1759 ff), and the antimicrobial activity of silver–NHC complexes against biosafety level 3 bacteria typifies the latter (W. J. Youngs et al.; p. 1739 ff). Mr. François Nicks is acknowledged for drawing the “crabene”. The editorial office thanks all authors for their excellent contributions to this cover picture puzzle. Finally, there are many gaps. EurJIC hopes that this issue will stimulate you to discover another fragment that will complete the picture.