We show that giant nonequilibrium fluctuations are present during the fret:
diffusive remixing occurring in ordinary liquid mixtures and in macromolec
ular solutions. The static structure factor of the fluctuations is measured
by using a quantitative shadowgraph technique. We show that structure fact
ors at different times and from different samples can be rescaled onto a si
ngle master curve without any adjustable parameter, thus giving strong evid
ence that nonequilibrium fluctuations are a universal feature of free diffu
sion processes.