Accretion flows light up the regions of extremely curved spacetime around
black holes, transforming the darkest objects in the Universe to the
brightest. Astrophysical black holes come in two distinct size scales,
with supermassive black holes powering the distant quasars, shaping galaxy
formation and the growth of structure in the early Universe, while stellar
mass black holes form in the last stages of stellar evolution of massive
stars. While there is a large range of mass (and presumably spin) in the
AGN, the stellar mass binaries form a remarkably homogeneous set so
provide a perfect laboratories for studying black hole accretion flows.
Yet the properties of the accretion flow should be fairly scale invariant,
so what we learn about accretion flows from stellar mass systems should
also be applicable to the supermassive black holes. I will review recent
progress in understanding Galactic binary systems, in particular how the
bewildering variety of spectral, timing and jet properties - the so called
'spectral states' - can be explained by changing the nature (and hence
geometry) of the accretion flow, and then discuss how these apply to AGN. (Host Magnus Axelsson)