Recently 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.