A system in determining a viscoelastic modulus of a sample, the system comprising: an optical illumination portion configured to deliver light to the sample; an optical data acquisition portion including an optical detector configured to receive light, that has been delivered to the sample by the optical illumination portion and that has interacted with the sample, to acquire optical data representing scattering of said light by multiple light-scattering events within the sample; and a processor operably cooperated with said optical data acquisition portion and programmed to: determine a diffuse remittance profile derived from the optical data, determine a pattern of the DRP as a function of angle in a plane of an optical detector, determine an average size of the light-scattering particles causing the multiple light-scattering events within the sample by comparing a first value with a map of second values, the first value defined by a distribution of light irradiance in said pattern, and the second values characterizing distributions of light irradiance across radiant flux profiles that have been theoretically calculated as functions of (i) a first variable representing average sizes of light-scattering particles and (ii) a second variable representing refractive index mismatch between the light-scattering particles and a medium containing said particles, calculate a mean square displacement value for said light-scattering particles and a viscoelastic modulus of the sample from the optical data, said MSD being a function of said size. an optical illumination portion configured to deliver light to the sample; an optical data acquisition portion including an optical detector configured to receive light, that has been delivered to the sample by the optical illumination portion and that has interacted with the sample, to acquire optical data representing scattering of said light by multiple light-scattering events within the sample; and a processor operably cooperated with said optical data acquisition portion and programmed to: determine a diffuse remittance profile derived from the optical data, determine a pattern of the DRP as a function of angle in a plane of an optical detector, determine an average size of the light-scattering particles causing the multiple light-scattering events within the sample by comparing a first value with a map of second values, the first value defined by a distribution of light irradiance in said pattern, and the second values characterizing distributions of light irradiance across radiant flux profiles that have been theoretically calculated as functions of (i) a first variable representing average sizes of light-scattering particles and (ii) a second variable representing refractive index mismatch between the light-scattering particles and a medium containing said particles, calculate a mean square displacement value for said light-scattering particles and a viscoelastic modulus of the sample from the optical data, said MSD being a function of said size. determine a diffuse remittance profile derived from the optical data, determine a pattern of the DRP as a function of angle in a plane of an optical detector, determine an average size of the light-scattering particles causing the multiple light-scattering events within the sample by comparing a first value with a map of second values, the first value defined by a distribution of light irradiance in said pattern, and the second values characterizing distributions of light irradiance across radiant flux profiles that have been theoretically calculated as functions of (i) a first variable representing average sizes of light-scattering particles and (ii) a second variable representing refractive index mismatch between the light-scattering particles and a medium containing said particles, the first value defined by a distribution of light irradiance in said pattern, and the second values characterizing distributions of light irradiance across radiant flux profiles that have been theoretically calculated as functions of (i) a first variable representing average sizes of light-scattering particles and (ii) a second variable representing refractive index mismatch between the light-scattering particles and a medium containing said particles, calculate a mean square displacement value for said light-scattering particles and a viscoelastic modulus of the sample from the optical data, said MSD being a function of said size.