Multi-wavelength fast correlated variability of black-hole X-ray binaries

The advent of new technologies permits high time resolution studies of X-ray binaries (traditionally performed in X-rays) also in the infrared and optical (O-IR) bands. This represents a breakthrough which allows us to study through timing techniques the physical connections among the different emitting components. Not by chance, in the last ten years fast O-IR photometry applied to black hole X-ray binaries has revealed to be one of the best ways to probe the jet in its innermost regions and its connection with the inflow. In this seminar I will review the major findings in this field, showing also the main results from the latest multiwavelength observing campaigns of the black-hole transient GX 339-4.