Since his student
years Grishchuk was
interested in different
aspects of cosmology
and gravitational waves
physics. In 1967, SAI,
Grishchuk defended the
thesis entitled "On the
problem of singularities in
Einstein's equations
solutions". Perhaps the most famous works of Leonid Petrovich was related to the problem of gravitational waves generation and their interaction with matter, fields and quantum systems. The work of the inevitability of the generation of gravitational waves in the early stages of expansion of the universe was of particular importance. These papers served as the starting point of a huge number of further studies on the generation various perturbations in the universe. Currently, the detection of cosmological gravitational waves is one of the most striking challenges for the observational cosmology. Grishchuk papers on the theory of interaction of gravitational waves with electromagnetic ones were useful to design detectors such as LIGO. Contribution of Leonid Petrovich Grishchuk to science can be definitely called great.