The impact of light scattering from dust in the micrometric size range is ubiquitous, from climate change to nanotechnology. While Lorenz-Mie scattering and effective medium approximations are currently the main theoretical tools adopted in the field, their effectiveness has been called into question. The accuracy in describing the optical properties of non-spherical, inhomogeneous particles is still inadequate in many applications.  Numerical computation is generally required, that is very demanding. This work examines on an experimental basis how shape and internal structure affect the scattering parameters. A particle-by-particle approach is exploited to analyse Antarctic, Greenland and Alpine ice cores, and a study of colloidal aggregates as a model for complex particles is also performed. The poor agreement of effective medium approximation to fit experimental data is shown to result from the contribution of correlations among the inhomogeneous fields radiated within the particle. Experimental findings are supported by extensive simulations. On the theoretical side, an interpretation on a molecular basis in terms of the structure factor is shown to be in accordance to data without any free parameter. The insights of this thesis are relevant for the quantitative assessment of the direct radiative effect of aeolian mineral dust on climate in the past, and for the interpretation of ongoing air monitoring campaigns in urban sites and in Antarctica.weiterlesen