Electron-electron correlation in strong laser fields

In the context of strong field-matter interaction, an increasing number of phenomena has been found to be not understood within the single-active-electron approximation. For such phenomena, electron-electron correlation plays an important role in the underlying dynamics. In this review, we will provide a broad overview of electron-electron correlation and examine two distinct cases of its manifestation in strong field physics. In the first example, we examine nonsequential double and multiple ionization of atoms, discussing the experimental manifestation of the electron correlation and the theoretical models that have been developed to describe the effect. The second case examines the interaction of larger systems with intense laser fields, for which multielectron effects have to be invoked for an accurate description of the dynamics.