The origin of Rutherford backscattering spectrometry (RBS) constitutes one of a handful of paradigm breaking physics experiments done in the early twentieth century that paved the way to modern physics and our conception of matter. From fundamental research in nuclear physics, RBS developed into a very useful material characterization technique for investigation of thin film composition, depth profiling of impurities, and thickness measurement in the nanometer range. This chapter introduces the foundation for the technique and how it is applied in modern materials analysis.