Diquark and doubly charmed tetraquarks $T_{cc}$

In this talk, we will provide a briefly introduction of the internal structures and dynamics in four-quark states in the constituent quark model. Different structure and dynamics of Diquarks are also briefly reviewed. Two parameters in the Semay-Silvestre-Brac potentials are fixed by two key exotics $X(3872)$ and $T_{cc}(3875)$ which are assumed as the hidden charmed $J^{PC}=1^{++}$ ground state tetraquark made from a $cq$ diquark and an $\bar c\bar q$ antidiquark and a doubly charmed $J^P=1^+$ tetraquark made of a $cc$ diquark and an $\bar u\bar d$ antidiquark. The masses of some diquarks and doubly charmed tetraquarks are calculated in terms of these potentials.