This volume contains eight contributions focusing on important conceptual trends in atomic and molecular theory. The `polarization' between ab initio and semiempirical methods is thoroughly analyzed in two of the articles, which also provide bridges between such procedures. Hydrogen transfer theory and electron delocalization are treated in two further papers. Explicitly time dependent descriptions of intermolecular dynamics, which constitute a characteristic trend in current research, is represented by an article about the quantum dynamics of diatoms in external fields. An unusual view of certain atomic excited states is presented in a paper on collective and independent particle character, and a new theoretical tool is surveyed in an article on dimensional scaling. The final article analyzes density functional theory from an unusual point of view. This book, which is a companion volume to Conceptual Trends in Quantum Chemistry, edited by E.S. Kryachko and J.L. Calais, ISBN 0-7923-2621-0, is for researchers and scientists in physics and chemistry from both industry and academia.