  We propose a simple way to perform three-dimensional (3D) rotational
microrheology using two-dimensional (2D) video microscopy. The 3D rotational
brownian motion of micrometric wires in a viscous fluid is deduced from their
projection on the focal plane of an optical microscope objective. The
rotational diffusion coefficient of the wires of length between 1-100 \mu m is
extracted, as well as their diameter distribution in good agreement with
electron microscopy measurements. This is a promising way to characterize soft
visco-elastic materials, and probe the dimensions of anisotropic objects.
