Accreting black hole binaries have been in focus of the X-ray
telescopes for the last half a century. Yet, radiative mechanisms leading
to a formation of the high energy photons along with the accretion flow
geometry in these objects are still being debated. Recent discovery of
complex interconnection of the optical and X-ray light-curves opened a new
path to explore physical processes operating in these objects. A number of
observables such as high optical luminosity, rapid variability and presence
of quasi-periodic oscillations at these wavelengths as well as complex
optical/X-ray cross-correlation cannot be explained in terms of the
standard accretion disc model. I will describe how the whole set of these
properties can be explained in terms of the hot accretion flow model.