Abstract gem-Diboron compounds are important intermediates in organic synthesis. In recent decades, a variety of methods for the preparation of gem-diboron compounds have been developed, among which, insertion into B–B bonds represents a unique approach. This chapter summarizes the synthesis of gem-diboron compounds based on insertion reactions into diboron compounds. These reactions include the diborylation of gem-dibromides, alkenes, benzylic C–H bonds, carbonyls, carbamates, and diazo compounds.