Recent discussions about the microstructure of materials generally focus on the ontological aspects of the molecular structure. However, there are many types of substances that cannot be studied by means of the concept of molecule, for example, salts. For the quantum treatment of these substances, a new particle, called phonon, is introduced. Phonons are generally conceived as a pseudo-particle, that is, a mathematical device necessary to perform calculations but which does not have a "real" existence. In this context, the aim (...) of this paper will be to analyze the ontological status of phonons. For such purposes we will critically analyze the arguments that would account for the presumed nonexistence of phonons. Finally, having already demonstrated that there are not enough reasons to consider phonons as non-existing entities, we will explore some possibilities that allow us to elucidate their ontological status. (shrink)