This is a copy of the slides presented at the meeting but not formally written up for the volume.

Ferromagnetism and superconductivity are long range ordering principles with a mutual exclusion in homogeneous systems. However, if they are spatially separated as in thin film heterostructutres and superlattices both properties are appearing simultaneously and their interaction can be studies. Heterostructures and superlattices consisting of the half-metal ferromagnet La0.67.Ca.33MnO3 and superconducting YBa2Cu3O7 layers were fabricated by pulsed laser deposition techniques and their magnetic as well as electronic interaction studies by a variety of techniques ranging from transport measurements to magnetic, neutron diffraction and XMCD analysis. It turns out that at the interface interaction effe3cts are taking place at two different length scales. One is based on the self - injection of spin-polarized quasiparticles with a length scale of ~ 10nm, the other is a short range exchange interaction with a length scale of ~ 3 nm. Furthermore, it could be shown that an so far unknown coupling of adjacent magnetic layers occurs when the superlattices are cooled through the superconducting transition temperature. The paper describes the RHEED- controlled growth of the superlattices as well as the relevant physics occuring at the interface.