While its connection to third phase formation has been implicitly understood in the litera-ture, we have only recently proposed that the mechanism of aggregation is associated with the liquid-liquid critical point. Here, we demonstrated this explicit relationship by quantifying organic phase structure over a wide composition range for binary extractant/diluent mixtures. We find that structure in these simple binary systems are dominated by critical fluctuations that are characterized by 3D Ising exponents. Molecular dynamics simulations are consistent with this mechanism of extractant aggregation, showing a lack of characteristic aggregate size.