The observation of the unexpected XYZ resonances has challenged the ordinary heavy quarkonium framework, and their microscopic nature remains an unsettled topic.
We review the status of the multiquark phenomenology.
We show how amplitude analysis can distinguish the possible scenarios of a QCD state, virtual state, or a kinematical enhancement, helping to solve the controversy. We will also comment on a recent controversy about the interpretation of the large prompt production cross-section of the X(3872).