Every serious student of chemistry should try to develop a `feel' for the way molecules behave - for the way they are put together and especially for the rules of engagement which operate when molecules meet and react. This primer describes how stereoelectronic effects control this behaviour. It is the only concise text on this topic at an undergraduate level. This is an important subject area and the comprehensive yet concise coverage in this book shows students how to build up a powerful but simple way of thinking about chemistry.