A fluid characterization measuring instrument comprises a sample vessel (14) for a bulk complex sample fluid having a capacity that is substantially larger than a domain size of the complex sample fluid and that is sufficiently large to cause bulk scattering effects to substantially exceed surface effects for the complex fluid sample, a coherent light source (12) positioned to illuminate the bulk complex sample fluid in the sample vessel and a first fibre (16) having a first end positioned to receive backscattered light from the sample after it has interacted with the sample. The first fibre is positioned close enough to an optical axis of the coherent light source and to the sample vessel to substantially decrease a contribution of multiply scattered light in the backscattered light. The instrument further comprises a first photon-counting detector (20) positioned to receive the backscattered light from a second end of the fibre, correlation logic (22) responsive to the first photon-counting detector and single-scattering fluid property analysis logic responsive to the correlation logic and operative to derive at least one fluid property for the sample fluid.