The aim of this book is to survey a number of chemical compounds that chemists, both theoretical and experimental, find fascinating. Some of these compounds, like planar carbon species or oxirene, offer no obvious practical applications; nitrogen oligomers and polymers, in contrast, have been touted as possible high-energy-density materials. What unites this otherwise eclectic collection is that these substances are unknown and offer a challenge to theory and to synthesis. It is envisioned that this collection of idiosynchractic molecules will appeal to chemists who find the study of chemical oddities interesting and, on occasion, even rewarding. "A great romp through imagined molecules, a challenge to the talents of synthetic chemists! Errol Lewars leads us expertly through a wonderland of the chemical imagination, fascinating molecular structures that do not (yet) exist!" Prof. Roald Hoffmann - Nobel Laureate, Chem. 1981- Cornell University, New York, USA "This book is an educational and enjoyable read, devoted to species on the fringes of chemical, calculation and conceptual plausibility" Prof. Joel Liebman, University of Maryland, Baltimore County, USA.