Extracting chemical information from modern wave functions and from experimental high-resolution electron densities is a challenging but valuable task. Many chemical concepts have been introduced at an intuitive level, often in the distant past, and hence need to be continuously confronted and scrutinised against a wealth of data obtained from modern computer calculations and increasingly automated X-ray equipment. This new book looks at the issues involved in bridging the expanding gap between widely used chemical concepts and modern accurate physical and computational data on molecules. It offers a valuable insight into research and opinion regarding this topic. Faraday Discussions document a long-established series of Faraday Discussion meetings which provide a unique international forum for the exchange of views and newly acquired results in developing areas of physical chemistry, biophysical chemistry and chemical physics. The papers presented are published in the Faraday Discussion volume together with a record of the discussion contributions made at the meeting. Faraday Discussions therefore provide an important record of current international knowledge and views in the field concerned.