This chapter gives a short introduction to the theoretical foundations of molecular quantum dynamics. The basic concepts for describing quantum mechanically the correlated motion of electrons and nuclei are discussed. The emphasis is put on presenting an ab initio methodology allowing a description of the ultrafast, pure electron dynamics triggered by ionization of a molecule—a process known as charge migration. Analysis of the basic mechanisms of the correlation-driven charge migration is provided together with some explicit examples. Finally, the concept of manipulating the chemical reactivity of a molecule by controlling the initially created, pure electronic coherences by ultrashort laser pulses, or the paradigm of the ”attochemistry”, is presented and discussed.