The aim of our proposal is to study the purely magnetic microstructure of Ni-Mn-In Heusler alloys on a mesoscopic microstructural length scale (1-300 nm) by means of magnetic SANS. In order to disentangle the nuclear coherent scattering signal from the magnetic contribution, we will make use of the recently developed so-called POLARIS technique (1D polarization analysis). By means of POLARIS, it becomes possible to access all three magnetization Fourier components as a function of temperature and applied magnetic field. We are not aware that such an experiment has been carried out on Ni-Mn-In Heusler alloys, and we believe that, besides improving our understanding of the POLARIS technique, it will provide fundamental insights into the underlying mechanism of magnetic SMA; in particular, we will be able to prove or disprove a recently proposed core-shell-type spin structure for this type of material.