To understand the nature of the problem, the principles of these techniques should be reconsidered. NMR studies the behaviour of the nuclei of a molecule when subjected to an externally applied magnetic field . The problem with this is that 1 H NMR, commonly referred to as proton NMR, only reveals the hydrogen atoms in the compound and does not provide information about the carbon skeleton and the other elements present in the sample, such as oxygen or nitrogen. If the structure is very complex or 1 H NMR is not sufficient to fully characterize the sample, additional NMR experiments must be performed for each nucleus.