Magnetic resonance force microscopy (MRFM) is a new microscopy technique that combines the spin selective detection of nuclear or ESR with the high spatial resoln. of at. force microscopy. The authors present MRFM measurements on a three-layer system in the micron range. The authors detected the 1-dimensional distribution of proton spins in a sample that consisted of two-ammonium sulfate layers and an intermediate layer of sodium chloride. The expts. were done at room temp. and normal pressure, in contrast to earlier MRFM measurements that were carried out in vacuum at room temp. or low temps.