With the Laboratory for Low Temperature Physics at the University of Massachusetts at Amherst, I am studying mixtures of the two stable isotopes of helium, 3He and 4He, at low temperatures, 0.03 < T < 0.5 Kelvin. The majority of our studies concern thin helium films, of a few atomic layers, thus the realization of a two-dimensional system. At temperatures below 2.2 Kelvin, 4He becomes a superfluid, a frictionless fluid; we explore the properties of the superfluid film by propagating third sound waves, temperature and density fluctuations, across the surface. At the temperatures of our study, the isotope 3He is not superfluid; the superfluid 4He, in bulk or in two dimensions, is an excellent vehicle for small amounts of 3He, since the 3He has little interaction with the superfluid 4He. Thus, for low concentration mixtures, the 3He acts as a nearly ideal Fermi gas. We study the properties of this Fermi gas in two and three dimensions with Nuclear Magnetic Resonance (NMR).