 ARPES has been used to map the occupied band structure of many metals and semiconductors, states appearing in the projected band gaps at their surfaces,quantum well states that arise in systems with reduced dimensionality, one-atom-thin materials like graphene and transition metal dichalcogenides, as well as many flavors of topological materials.It has also been used to map the underlying band structure, gaps, and quasiparticle dynamics in highly correlated materials like high-temperature superconductors and materials exhibiting charge density waves.When the electron dynamics in the bound states just above the Fermi level needs to be studied, two-photon excitation in so-called pump-probe setups (2PPE) is used.