Peripheral conjugate carbo- and heterocycles such as bridged homo- and heteroannulenes, cyclazines, and dihydropyrenes are desired in order to obtain experimental evidence regarding our recognition of the net energy changes associated with π-electron delocalizations. In this review is described the chemistry of cyclazines, a novel class of compounds consisting of a π perimeter bridged by a central sp2-hybridized nitrogen atom; 1. Introduction, 2. Synthesis and Properties of Cyclazines, 3. Reactions of Cyclazines, 4. Molecular Orbital Treatment of Cyclazines and Electron Paramagnetic Resonance Study of Their Radical Ions.