About the $J\text{\hspace{0.17em}⁣}\mathrm{/}\text{\hspace{0.17em}⁣}\psi J\text{\hspace{0.17em}⁣}\mathrm{/}\text{\hspace{0.17em}⁣}\psi$ peak of LHCb: fully-charmed tetraquark?

We discuss the interpretation of the $J\text{\hspace{0.17em}⁣}\mathrm{/}\text{\hspace{0.17em}⁣}\psi J\text{\hspace{0.17em}⁣}\mathrm{/}\text{\hspace{0.17em}⁣}\psi$ peak recently seen by the LHCb collaboration at CERN, and take the opportunity to review the experimental and theoretical state of the art for exotic hadrons. It is stressed that in constituent models, the states in the continuum require a dedicated treatment to single out resonances atop the continuum.