Abstract: On July 29 2021 the LHCb Collaboration announced the discovery of a new type of exotic hadron -- a doubly-charmed tetraquark $T_{cc}^+$, whose mass agrees precisely with a 2017 theoretical prediction.  I will discuss the recent related experimental and theoretical developments regarding new types of hadrons involving heavy quarks: tetraquark and pentaquark hadronic molecules, doubly heavy baryons, stable tetraquarks and others.