  We demonstrate focusing and imaging through a scattering medium noninvasively
by using wavefront shaping. Our concept is based on utilizing the spatial
fluorescence contrast which naturally exists in the hidden target object. By
scanning the angle of incidence of the illuminating laser beam and maximizing
the variation of the detected fluorescence signal from the object, as measured
by a bucket detector at the front of the scattering medium, we are able to
generate a tightly focused excitation spot. Thereafter, an image is obtained by
scanning the focus over the object. The requirements for applicability of the
method are discussed.
