The experimental and theoretical aspects of obtaining the magnetic information carried by laser beams diffracted from an array of nanosized magnetic objects are reviewed. Experimentally it will be shown that the magneto-optic Kerr effect (MOKE) hysteresis loops recorded for diffracted beams can be quite different from those recorded for the reflected beam. We will show that the diffracted MOKE (D-MOKE) loops are proportional to the magnetic form factor or, equivalently, to the Fourier component of the magnetization corresponding to the reciprocal lattice vector of the diffracted beam. In conjunction with micromagnetic simulations, the D-MOKE provides a powerful and non-destructive technique for investigating the magnetization reversal process in submicron-sized magnetic particles. The advantages and disadvantages of the D-MOKE technique will be compared to those of other techniques that yield related information (e.g. magnetic force microscopy, Lorentz electron microscopy and micromagnetic simulations).