To solve the equation of motion for a quantum-mechanical wavefunction $\psi$ the Schrödinger equation, for a many-particle system is a major problem in many branches of physics. Based on the idea that the joint probability density $|\psi|^2$ can be written as the product of a marginal probability density (that depends only on some of the particle variables) and a conditional probability density, it can be shown that there exists a marginal wavefunction which also obeys a Schrödinger equation, but with an effective potential that encodes the interaction with all parti- cles. In this talk, I present an application of this idea to a many-electron system: By taking only the variables of one electron as the marginal coordinates, an exact single-electron picture that describes the correlated electron dynamics of many electrons is obtained. All many-electron interactions are then encoded in the structure and time-dependence of an effective single-electron potential. This approach is applied to the description of strong field phenomena, because they are often interpreted in a single-electron picture, while at the same time the understanding and measurement of many-electronic interactions is a main topic in this field. First results for 2- and 3-electron model systems in strong laser fields are presented and used to illustrate how an exact single electron picture of ionization or high-harmonic generation looks like. Additionally, I show first steps towards a feasible method for the calculation of the many-electron dynamics in complex molecules. <br/><br/> [1] Axel Schild, E.K.U. Gross, Phys. Rev. Lett. 118, 163202 (2017).