Method for determining an aggregation state of a solute in a solvent, comprising: illuminating (702), with a laser source, at least one mixture comprising the solute and the solvent with a pulsed laser beam, detecting (704), with a detector, a portion of the pulsed laser beam, wherein the portion of the pulsed laser beam has interacted with the at least one mixture, characterized in that detecting (704) a portion of the pulsed laser beam comprises: detecting non-resonant second harmonic photons, wherein the non-resonant second harmonic photons issue from an interaction of the pulsed laser beam with the solvent of the at least one mixture, and determining (706) at least one value indicative of the non-resonant second harmonic photons detected for the at least one mixture, and in that the method further comprises: determining (708) at least one characteristic for an aggregation behavior of the solute in the solvent on the basis of the at least one value indicative of the detected non-resonant second harmonic photons determined for the at least one mixture. A computer readable medium and an apparatus (300, 400, 500, 600) are described.