During combustion of fossil fuels soot particles form as a byproduct when a sufficient amount of oxygen is not present to yield a complete conversion of fuel into major combustion products such as carbon dioxide and water vapour. The soot particles (unburnt carbon) significantly affect the performance and durability of many engineering systems such as gas turbines and diesel engines and are the cause of significant human health problems associated with the respiratory system. Environmentally, the emissions of soot particles from combustion systems are also harmful as they contribute to the global warming. This book covers the important technological issues related to the formation, nanostructure, modelling, health effects, reduction and impact of soots.