Figure shows this analysis for nanoparticle gels at U 0 = 10k B T and Figure for attractive fluids at U 0 = 3k B T . Nanoparticles are colored by their resonant frequency, with low frequency resonators in red and high frequency resonators in blue. If we consider all the particles in the gel (Figure ), the structure is isotropic as indicated by the two-dimensional structure factor S(q) comprising circles and rings (Figure ). If we consider only the reddest ≈ 25% of particles (Figure ), we observe that these resonators are found collectively in 1-D structures oriented parallel with the field polarization Ê0 . This one-dimensional alignment with Ê0 is quantified with a "butterfly" pattern in S(q) (Figure ). These butterfly patterns are analogous to those observed in 1-D alignment of colloidal gels into "logs" in shear flows. If we consider only the bluest ≈ 20% of particles (Figure ), we observe that these resonators are found collectively in structures oriented orthogonal to Ê0 , with no preference for either of the two orthogonal directions. This isotropic alignment orthogonal to Ê0 is quantified with an ellipse pattern in S(q) (Figure ). These collective resonating structures are not encoded solely by the gel structure itself, but by the interaction between structure and incident light. Though the gel structure itself is isotropic, for a given Ê0 , gel strands will have a particular orientation relative to Ê0 that affect ω res,i . Particles in stands oriented parallel to Ê0 resonate at lower frequencies (red), while orthogonal strands resonate at high frequencies (blue). The spectrally selective anisotropy is particularly noticeable when changing the polarization direction from x-polarized in Figure -8C to y-polarized in Fig- . Though the gel structure is identical, the red strands for y-polarized light are rotated 90°relative to those for x-polarized light, and similarly for the blue strands. Both have identical S(q) when the components of q are represented as parallel and perpendicular to Ê0 . These phenomena agree very well with those observed in simulations of small fractal clusters of closely-spaced gold nanoparticles, where the local near-field enhancement is concentrated to field polarization-aligned chains at low frequencies. p (34% of all nanoparticles). (D)-(F) Structure factor S as a function of wavevector components parallel q ∥ and perpendicular q ⊥ to Ê0 computed among all nanoparticles (D), among only "red" nanoparticles (E), and among only "blue" nanoparticles (F).