The particle resonant frequencies are not distributed randomly in space throughout the assembled microstructure, but rather show strong spatial correlations. For example, the nanoparticle gel (Figure ) is structurally isotropic, evidenced by its isotropic twodimensional structure factor S(q). However, when the gel is illuminated with light linearly polarized in the E 0 direction, the "red" particles resonating at lower-than-average frequencies are found primarily in strands of the gel aligned with E 0 . This results in the butterfly pattern in the 2D structure factor whose "wings" orient in the component of the wavevector q ⊥ orthogonal to the electric field. Similarly, "blue" particles resonating at higher-than-average frequencies are found primarily in strands aligned orthogonal to E 0 , resulting in an ellipse pattern in S(q) aligned in the q ∥ direction parallel to E 0 .