Lawrence D. Guth continues MIT's graduate course 18.156, Projection Theory, with a lecture adapting the Fourier method to Euclidean space. Guth works through how to handle the method across many different scales, building on the harmonic analysis tools introduced earlier in the course. The lecture is chalkboard based, aimed at graduate students already comfortable with real and harmonic analysis, and fits into the course's broader study of projections, incidence geometry, and related problems in analysis. As part of a semester long sequence from MIT OpenCourseWare, this session assumes familiarity with prior lectures and builds technical machinery rather than offering a standalone survey. Expect dense notation and sustained derivation rather than illustrative examples, typical of an advanced MIT math seminar recorded for OCW distribution.