  Brilliance of novel gamma-ray Crystal-based Light Sources (CLS) that can be
constructed through exposure of oriented crystals to beams of
ultra-relativistic charged particles is calculated basing on the atomistic
scale numerical modeling of the channeling process. In an exemplary case study,
the brilliance of radiation emitted in a diamond-based Crystalline Undulator LS
by a 10 GeV positron beam available at present at the SLAC facility is
computed. Intesity of CU radiation in the photon energy range 10^0 - 10^1 MeV,
which is inaccessible to conventional synchrotrons, undulators and XFELs,
greatly exceeds that of laser-Compton scattering LSs and can be higher than
predicted in the Gamma Factory proposal to CERN. Construction of novel CLSs is
a challenging task which constitutes a highly interdisciplinary field
entangling a broad range of correlated activities. CLSs provide a low-cost
altenative to conventional LSs and have enomorous number of applications.
