NOE (Nuclear Overhauser Effect) is an important NMR measurement technique that can reveal spatial proximity relationships within molecules. In this column, we discuss the difference between difference NOE, 1D NOESY, and 2D NOESY, and how to select each method, the relaxation time that is key for analysis. The causes and solutions for cases when NOE is not detected are also covered. Moreover, we answer the frequently asked questions and explain the key points for effective use of NOE measurement.