Multicomponent nanoparticles are important in many fields, including catalysis, magnetics, plasmonics, and electronics, due to the chemical and physical properties that arise from the interactions between their components. The optimization of nanoparticles with desired functionalities requires the development of platforms for systematically studying a broad spectrum of compositions and structures. Combinatorial screening is a common strategy to establish such a composition-structure-function relationship. To achieve this goal, we developed scanning probe block copolymer lithography (SPBCL), a technique that allows one to generate nanoreactors consisting of polymers loaded with metal precursors, which upon thermal treatment can be converted into nanoparticles with sub-nm resolution. This technique has been successfully used to synthesize single metal, metal oxide, alloy, and heterostructured nanoparticles composed of metals including Au, Ag, Pd, Pt, Ni, Co, Fe, and Cu. When combined with polymer pen lithography (PPL), a high-throughput cantilever-free patterning technique that utilizes an elastomeric pen array with millions of pens, combinatorial libraries of nanoparticles can be made by varying the ink composition across a 1-million-pen array. The synergy between SPBCL and PPL allows an innovative and robust solution to synthesize new nanoparticles over large areas, which enables the rapid screening of the properties of multicomponent nanoparticles. This novel approach lays the foundation for generating new combinatorial libraries of materials, where scale, in addition to composition becomes an important library parameter.