Azulene 1, pentalene 2, and heptalene 3 are classical nonalternant hydrocarbons. Their fascinating π-frameworks, consecutive arrangements of odd-membered carbocycles, have engaged chemists’ attention for some time. In this review, we describe the salient revivals of these nonalternant hydrocarbons that are incorporated into polycyclic π-systems. Historical landmarks, recent studies, and fundamental properties, as well as potential applications to functional organic materials, are documented.