Crystal Research and TechnologyVolume 55, Issue 5 2070019 Cover PictureFree Access Modularity: The Japanese Pioneering Contribution to the Investigation of Modular Structures (Crystal Research and Technology 5/2020) First published: 07 May 2020 https://doi.org/10.1002/crat.202070019AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Abstract In article number 1900045, Akihiro Umayahara and Massimo Nespolo present a revised classification of monoarchetypal modular structures. Chemical twins are characterized by altered coordination at the interface between modules and, depending on whether this results or not in a modification of the chemical composition, they are classified in heterochemical and isochemical. Polytypes in which the partial operations mapping the modules are ordinary space-group operations are called Ito twins. OD structures are polytypes in which layer pairs are geometrically equivalent. Volume55, Issue5Special Issue: Mathematical Crystallography 2019May 20202070019 RelatedInformation