  This is a short review in honor of B. Mandelbrot's 80st birthday, to appear
in W ilmott magazine. We discuss how multiplicative cascades and related
multifractal ideas might be relevant to model the main statistical features of
financial time series, in particular the intermittent, long-memory nature of
the volatility. We describe in details the Bacry-Muzy-Delour multifractal
random walk. We point out some inadequacies of the current models, in
particular concerning time reversal symmetry, and propose an alternative family
of multi-timescale models, intermediate between GARCH models and multifractal
models, that seem quite promising.
