In recent years, the density-matrix renormalization group (DMRG) method, by now the leading method for one-dimensional
strongly correlated quantum systems, has been extended to the simulation of time-dependent phenomena at finite-temperature
and is therefore now ideally placed to calculate momentum- and frequency-dependent scattering off magnets. In this talk, I will introduce
to the method, its relation to the theory of entanglement, the important post-processing of data, and show how if produces results in
excellent agreement with various experimental results (for instance, RbCoCl3) and allows the detailed study of magnetic properties of materials.