In this doctoral research a Zeeman decelerator was employed to obtain precise control over magnetic particles and prepare them for cold and controlled molecular collision experiments in a crossed-beam setup. Combined with an improved velocity map imaging apparatus and novel recoil-free ionization schemes employing ultraviolet and vacuum-ultraviolet lasers, this allowed to image the collision outcome for these particles with extraordinary precision and at collision energies that extend to below 1 K. Thus, elusive quantum mechanical effects were observed. These include fine oscillations in the angular scattering distributions that originate from the wave-character of the particles (diffraction oscillations) and rapid changes of the collision outcome around specific collision energies (scattering resonances). The measurements were in excellent agreement with theoretical predictions. However, some discrepancies exist that can potentially challenge the used theoretical models. These results underline the prospects for further high-precision investigations of scattering processes that put these quantum scattering models to the test and increase the chemical diversity in controlled scattering experiments. This can ultimately help to gain a detailed understanding of molecular interactions.