Future HEP experiments at the energy and intensity frontiers require fast inorganic crystal scintillators with excellent
radiation hardness to face the challenges of unprecedented event rate and severe radiation environment. This paper
reports recent progress in application of very fast inorganic scintillators in future HEP experiments, such as thin layer of
LYSO crystals for a shashlik sampling calorimeter and a precision TOF detector proposed for the CMS upgrade at the
HL-LHC, undoped CsI crystals for the Mu2e experiment at Fermilab and yttrium doped BaF2 crystals for the proposed
Mu2e-II experiment. Applications for Gigahertz hard X-ray imaging will also be discussed.