One of the emerging question of science is how are complex things made from simple things? Larger is not necessarily more complicated than their smaller subsystems. In biology, chemistry and materials science the issue is how to understand large molecules in terms of atoms. In atomic physics one may strive to understand properties of many electron systems in terms of single electron properties. The general theme is interdependency of subsystems, or `correlation'. Electron correlation dynamics is a central theme of this talk. The dynamics of electron correlation may affect single electron transitions. However, this effect is sometimes difficult to separate from other effects. Correlation is usually dominant in multiple electron transitions for fast collisions since there is not enough time for the collision partners to interact more than once. This means that multiple electron transitions in fast collisions provide an unobstructed view of the dynamics of electron correlation. Examples include double ionization of helium and other multiple electron transitions in interactions of atoms, molecules and earthworms in collisions with light and matter.