[en] The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO₂ is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the diffraction pattern, information about the molecular structure can be gained. This is illustrated with the example of laser-aligned naphthalene molecules (C₁₀H₈). Furthermore, I demonstrate that the quality of the molecular alignment is essential for the reconstruction of the molecular structure. In the second part of this work, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond and the few-femtosecond regime. Although a one-particle picture has been successfully applied to many ionization processes, important many-body effects do constantly occur. Based on a time-dependent configurationinteraction singles (TDCIS) approach, I study the temporal behavior of these many-body effects. During the photoionization of atomic xenon, unexpected correlation effects between the ionized electron and the ion occur. This electron-ion entanglement results in a reduced coherence within the ion. Populations and coherences of the ionic states are probed with attosecond precision using transient absorption spectroscopy. Even the subcycle ionization dynamics can be studied with this technique. Here, field-driven dressing effects between the ion and the freed electron appear, which I investigate on atomic krypton. Interactions between the ion and the electron, which modify the ionic states, occur also in high-harmonic generation (HHG). They are visible in the HHG spectrum as my studies of argon and xenon show. All these examples demonstrate on the one side, ultrashort pulses can be used to initiate complex electronic, atomic, and molecular motions. On the other side, it is also possible to probe and to control these dynamical processes with ultrashort pulses.