Positional Disorder: Nanocrystal Linker Gels Plasmonic nanoparticle gels are disordered percolating networks of linked metal or metal oxide nanoparticles with porous, solvent-filled interstitial spaces. These materials can exhibit collective plasmon resonances reflecting how near-field coupling in the network hybridizes the localized surface plasmon resonances (LSPRs) of individual nanoparticles. A consequence of the strongly attractive interactions required to form system-spanning colloidal networks is that gelation often manifests as a nonequilibrium process that competes with other assembly outcomes, including macroscopic phase separation, aggregation, and precipitation. In nonequilibrium gels, the network structure and properties can depend sensitively on the gel formation pathway and even change over time as the gel ages. These factors present challenges to designing plasmonic gels with targeted optical properties.