Nuclear magnetic resonance (NMR) is one of the most powerful spectroscopic techniques in analytical chemistry. It is an important tool for the studies of host–guest complexes, for elucidating the structures of the various complexes existing in the form of aggregates, ion pair or encapsulated systems. As the name suggests, NMR identifies the different nuclei in the molecules (most commonly, proton), by measuring their chemical shift. The binding activity of two molecules causes a considerable change in their electronic environments. This leads to a shift in the signals in the NMR spectrum, and this basic principle is made use of to study the phenomena of host–guest chemistry. The driving forces for host–guest binding are the various secondary interactions between molecules, such as hydrogen bonding and pi–pi interaction. Thus, NMR also serves as an important technique to establish the presence of these interactions in a host–guest complex.