The present invention relates to a method for the optical measurement of at least the stability and the aggregation of particles in a liquid sample which is located in a sample container, wherein the method comprises the following steps: irradiating the sample with light of at least one first wavelength in order to fluorescently excite the particles, irradiating the sample with light of at least one second wavelength in order to examine the scattering of the particles, measuring the fluorescence light which is emitted by the sample; and measuring the extinction light at the second wavelength, wherein the irradiated light of the second wavelength runs through the sample container, is reflected back, runs again through the sample container in the opposite direction and exits as extinction light, wherein the stability is determined based on the measured fluorescence light and the aggregation is measured based on the measured extinction light. The invention further relates to a corresponding apparatus.