For spherical nanoparticles, strategies utilizing vector spherical harmonics, e.g. generalized multiparticle Mie theory and transition-matrix (T-matrix) methods, or approaches utilizing vector/tensor electric and magnetic multipole moments, e.g. coupled dipole methods, are even more efficient. These computations scale well with system size to address assemblies with considerably more particles than discrete dipole approximation and boundary element methods. One implementation that combines the analytic T-matrix method for individual nanoparticle scattering with a scattering matrix formalism enabled simulation of large disordered configurations of spherical nanoparticles arranged in slabs and macrospheres (Figure ). Generalized multiparticle Mie theory has been used to quantify how defects modify the far-field and near-field properties of nanoparticle superlattices 4 and to simulate core-satellite nanoparticle cluster morphologies. The coupled dipole method was employed to map out the induced dipole strength of each nanoparticle in a finite superlattice (Fig- ), showing strong spatial dependence and significant edge effects. Coupled dipole methods have revealed chiroptical behavior in chiral nanoparticle clusters and two-layer superlattices and near-perfect optical reflectance or transmission in superlattices and vacancy arrays. To ensure that optical simulations consider experimentally representative nanoparticle configurations, it is advantageous to input structures produced from Monte Carlo, molecular dynamics, or Brownian dynamics trajectories of the assembling colloids. Through coarsegrained interactions, such simulations model physical and chemical features important for reproducing nanoparticle spatial correlations measured experimentally by SAXS. Recently, Sherman et al. introduced a mutual polarization method (MPM) for electromagnetic simulations tailored to accommodate large-scale configurations obtained from simulated colloidal trajectories. MPM is a variant of the coupled dipole method that constructs and solves a linear system of equations for the induced dipole and quadrupole moments within each nanoparticle when irradiated with light in the quasistatic limit. This system of equations is designed to yield an efficient and numerically stable solution for arbitrary particle configurations, including those with particle "overlaps" which occur in simulations with coarse-grained colloidal interactions. MPM utilizes a rapid, spectrally-accurate Ewald summation technique to incorporate (up to) triply-periodic boundary conditions, and it readily models assembled configurations containing up to O(10 5 ) nanoparticles. Electromagnetic simulations of this scale can be used to study the optical response of structurally and compositionally complex plasmonic assemblies, including gels, and metasurfaces. From an experimental perspective, challenges for studying disordered optical assemblies include ensuring nanomaterial synthesis and assembly are sufficiently well-controlled and characterized to model using simulation for improved mechanistic understanding. Progress in this direction has been evident in the study of self-assembled chains composed of metal nanospheres, nanocubes, and nanorods, whose far-and near-field optical properties are tunable based on nanoparticle shape, chain length, and attachment orientation (e.g., face-to-face versus edge-to-edge). Judicious selection of experimental parameters, such as the types and lengths of grafted polymers, solvent polarity, and assembly time, allow for precise manipulation of the interaction between building blocks to form stringy assemblies, as characterized by electron microscopy and predicted by coarse-grained modeling.