The nephelometer experiment carried on the Galileo probe was designed to measure the jovian cloud structure and its microphysical characteristics from entry down to atmospheric pressure levels greater than 10 bars. Before this mission there was no direct evidence for the existence of the clouds below the uppermost cloud layer, and only theoretical models derived from remote sensing observations were available for describing such clouds. Only one significant cloud structure with a base at about 1.55 bars was found along the probe descent trajectory below an ambient pressure of about 0.4 bar, although many indications of small densities of particle concentrations were noted during much of the descent.