Photoexcited spin-vibronic dynamics is the consequence of the interplay between nonadiabatic and spin-orbit couplings (SOCs) comprising several regimes, depending on the relative magnitudes of these couplings. It is of particular relevance for systems containing transition metals where large SOC comes to together with the metal's electronic structure and ligand effects giving rise to a large density of valence excited states. Due to their relevance for various practical applications, in particular first-row transition metals are a prime target of current research. Electronic excitations in transition metal complexes can be classified as being of metal/ ligand centered (MC/LC) or charge transfer type, e.g. metal-to-ligand charge transfer (MLCT) or vice versa (LMCT). Stepping from rather successful 4d/5d to 3d transition metals leads to a drastically altered electronic structure as far as the interplay between these types of transitions is concerned. This often comes along with a much reduced MLCT lifetime, which is disadvantageous, e.g. for catalytic applications. This is a challenge for ligand design and in particular systems with carbene ligands showed MLCT lifetimes in the nanosecond regime have been reported. The challenge to theory provided by first-row transition metal compounds is twofold.