The Wyatt miniDawn TREOS is a multi-angle light scattering detector (MALS), reading at three different angles. This instrument is capable of calculating molecular weights and average dimensions of macromolecules and complexes in solution with great accuracy. The system works in tandem with an Optilab refractometer with extended range (T-rEX), to determine the absolute concentrations of analytes. When coupled with gel-filtration chromatography, this MALS/T-rEX combination system can easily detect the molecular weight, spatial size, and concentration of macromolecules in mixed solutions. This allows users to identify, characterize, and determine relative abundance of complexes formed by mixed analytes, or the oligomerization states of single proteins. As currently operated, our system is suited to aqueous systems and relatively large molecules only.