The objective is to refine current understanding about the mechanism of hydrotropy with respect to polarity and electrostatic character of hydrotropes and hydrophobic solutes respectively 1. The question at hand: whether hydrophobic solutes are incorporated into micellar-like aggregates, or instead complexed (say 1:1 or other ratios) with the hydrotrope molecules? This proposal involves using hydrotropes from each of the three main classes (cationic, anionic, non-ionic, Figure 2) with two hydrophobic dyes of different polarity. This systematic study, covering the different elements of the hydrotrope-solute matrix, has been designed to shed new light on the mechanism of hydrotropy.