Abstract: This is the second talk on intersection cohomology and Donaldson-Thomas invariants of quiver moduli continuing a previous talk given by M. Reineke in May. The aim of this talk is to introduce the concepts and main notations of Donaldson-Thomas theory, in particular the Donaldson-Thomas sheaves which serve as a refined version of Donaldson-Thomas invariants. These sheaves are certain mixed Hodge modules on quiver moduli spaces.