The experimental investigations of the direct and the inverse proximity effects in superconductor- ferromagnet (SF) structures are the subjects of this book. The direct proximity effect was investigated by measurements of both critical temperature (Tc) and critical current (Ic) variations. Measurements were focused on ? ?phase shifts observed in the experiments and similarity of the Tc and Ic behavior in our experiments, such as the same periods of oscillations that correspond to equal magnetic lengths in ferromagnetic layers. One of the main findings in my thesis were the observations of the strong oscillations of the critical superconductor current and critical temperature with the period different from previously reported experiments. The inverse proximity effect in SF structures was measured by detecting the induced ferromagnetic order in the superconductor. One of the most important results of these experiments is the experimental observation of the "spin screening effect" which is intimately related to the formation of the triplet component in the superconductor condensate function.