Microrheology is a technique to mechanically characterize materials in an economic manner. For this reason it is used extensively in biophysics to study biological materials such as in-vitro cytoskeleton networks and the cytoplasm of live cells.

In the past year we have discovered a new regime of mechanical response of complex fluids via microrheology experiments. The length scale relevant for this new type of material response is surprisingly large, for actin networks in is in the range of 2-6 microns.