Ultimately, we want to obtain a kind of movie that shows how electrons, spins and crystal lattice of a solid interact with each other on their natural (typically femtosecond) time scales and at their natural (typically THz) resonance frequencies. This idea is illustrated by the schematic in Figure 1.

We are particularly interested in the flow of angular momentum and energy. Examples of questions we want to answer are as follows:

• How does the vibrating crystal lattice (phonons) affect the state of the electrons or spins and vice versa (see Figure 1)?
• How can electron spin and orbital angular momentum be transported through a solid by light pulses (see Figure 2)?
• How do molecules in liquids and soft matter rotate due to strong pulsed electric fields?