Infrared spectroscopy provides molecular information in systems that range from the level of peptides, isolate proteins and enzymes, to even more complex systems such as peptide–protein complexes and membrane‐bound proteins. The information may be a global one such as the secondary structure composition of a protein, or it may be highly specific such as the alteration of individual vibrating bonds in an enzyme. Furthermore, the structural information is not restricted to a static picture, but can also be obtained at high time resolution to allow true structure–function correlation. Illustrative examples are given to demonstrate the sort of information, which infrared techniques can provide and how this information can be extracted from the experimental data. In addition, strengths and limitations of the infrared approach are discussed. This should help the reader to evaluate whether a particular system is appropriate for study by infrared spectroscopy, and what specific advantages are gained when applying infrared techniques.