A third decade with continuously growing attention for the chemistry of N-heterocyclic carbenes (NHCs) is nearing its completion and new applications for this compound class are still being discovered. For example, NHCs are employed as versatile ligands within novel transition metal and main group element compounds; even complexes with lanthanides and actinides are now known. Also, the application of NHCs in organocatalysis has been proven as an attractive metal-free method for accessing value added products in an efficient manner. Due to the strong σ-donor ability of NHCs, they are commonly employed as ligands in organometallic catalysts and often boost the catalytic activity above NHC-free analogues (e.g. Grubbs' 2nd generation and Organ's PEPPSI catalysts). Meanwhile, the utilization of NHCs to intercept otherwise elusive main group compounds has greatly influenced the direction of modern main group chemistry. More recently, the related cyclic(alkyl)(amino)carbenes (cAACs), with enhanced π-acceptor character, has provided exciting new vistas of reactivity including the formation and study of novel molecular inorganic radicals. Moreover, NHCs have spun off new ligand systems such as N-heterocyclic olefins (NHOs), as well as N-heterocyclic imines (NHIs). Although the chemistry of these ligand classes are still in their infancy in comparison to that of NHCs, they have already shown great potential for the stabilization of compounds with low-valent main group elements in addition to the implementation of NHOs and NHIs as supporting ligands within organometallic catalysis. This Special Issue of Zeitschrift für Anorganische und Allgemeine Chemie (ZAAC) entitled “NHC-stabilization of reactive units in main group and transition metal chemistry” aims to showcase the recently developed applications with regard to this topic. The 15 contributions to this issue are written by some of the international leading researchers in this field. These articles range from the synthesis, structural characterization and reactivity of novel main group and transition metal complexes to their use in catalysis. We were able to collect a wide range of papers and may indulge the readership with the studies on Group 2 (Mg; one contribution), Group 7 (Mn; one contribution), Group 11 (Au; one contribution), Group 12 (Zn, Hg; two contributions), Group 13 (B, Al, Ga; four contributions), Group 14 (Si, Ge, Sn; four contributions), and Group 15 (N, P; two contributions) compounds. We would like to thank all authors for their contributions to this special issue. Also, all referees who evaluated the submitted manuscripts are gratefully acknowledged for their kind and essential advice and suggestions. Shigeyoshi Inoue Eric Rivard