Higher-order organization through mesoscale self-assembly and transformation of hybrid nanostructures is a key challenge in designing advanced materials. Current methods often rely on physical techniques rather than spontaneous chemical assembly across multiple length scales. This study highlights how aggregation and crystallization can lead to mesoscale self-assembly and cooperative transformation of hybrid inorganic-organic building blocks, producing single-crystal mosaics, nanoparticle arrays, and complex nanostructures. These processes are relevant to biomineralization models, where matrix-mediated nucleation occurs. The organization of matter and energy is fundamental to the universe, and chemistry bridges physics and biology by dealing with molecular-level ordering. Nanochemistry extends synthetic chemistry to exploit collective properties of organized assemblies. While many approaches mimic biological nanostructures, they lack the inherent materials-building properties of organisms. Strategies for long-range organization and assembly of nanostructured phases include chemical and microfabrication methods, as well as spontaneous processes like solvent evaporation and molecular cross-linking. A chemistry of organized matter can couple synthesis and self-assembly to produce complex higher-order structures. Different driving forces operate at various stages of synthesis, leading to emergent properties. Inorganic and organic building blocks can generate diverse structures due to disparate driving forces. The balance between self-organization forces and mutual coassembly determines whether phase-separated or nonequilibrium structures form. Crystallization and aggregation are key engines of construction from molecular to macroscopic scales. Kinetic control of nucleation and growth is crucial, with amorphous precursors transforming into crystalline intermediates. Surface adsorbed macromolecules and surfactants influence crystal texture and composition. Mesoscale self-assembly of inorganic-organic hybrid nanoparticles can produce stable or transformable structures. Aggregation-mediated crystallization is prominent in solids like iron oxides, cerium oxide, and copper oxides. Surface charge sensitivity and hydrolytic transformation affect nanoparticle aggregation and crystallization. The alignment of primary particles and their aggregation into continuous crystals is influenced by hydrothermal conditions and oriented attachment. Macromolecules can influence crystal habit through selective adsorption, leading to preferential growth inhibition. Soluble macromolecules and surfactants can significantly affect early stages of crystal growth. Aggregation-based pathways of crystal growth are influenced by polymer interactions, leading to textured single crystals. Strong binding interactions between macromolecules and nanocrystals can result in crystals containing significant levels of occluded organic molecules. Mesoscale self-assembly of nanoparticle arrays is influenced by surface-anchored surfactant molecules. Hydrophobic interactions drive assembly, often reversible unless stabilized by interparticle cross-linkers. Surfactant-coated nanoparticles with high shape anisotropy can self-assemble into ordered superstructures. The sensitivity of ordering transitions to interaction potentials between crystal surfaces and surfactant molecules is highlighted by microemulsion-based reaction fields. Polymer-induced nanoparticle assembly involves phase separation of hydrophilic and hydrophobic segments,Higher-order organization through mesoscale self-assembly and transformation of hybrid nanostructures is a key challenge in designing advanced materials. Current methods often rely on physical techniques rather than spontaneous chemical assembly across multiple length scales. This study highlights how aggregation and crystallization can lead to mesoscale self-assembly and cooperative transformation of hybrid inorganic-organic building blocks, producing single-crystal mosaics, nanoparticle arrays, and complex nanostructures. These processes are relevant to biomineralization models, where matrix-mediated nucleation occurs. The organization of matter and energy is fundamental to the universe, and chemistry bridges physics and biology by dealing with molecular-level ordering. Nanochemistry extends synthetic chemistry to exploit collective properties of organized assemblies. While many approaches mimic biological nanostructures, they lack the inherent materials-building properties of organisms. Strategies for long-range organization and assembly of nanostructured phases include chemical and microfabrication methods, as well as spontaneous processes like solvent evaporation and molecular cross-linking. A chemistry of organized matter can couple synthesis and self-assembly to produce complex higher-order structures. Different driving forces operate at various stages of synthesis, leading to emergent properties. Inorganic and organic building blocks can generate diverse structures due to disparate driving forces. The balance between self-organization forces and mutual coassembly determines whether phase-separated or nonequilibrium structures form. Crystallization and aggregation are key engines of construction from molecular to macroscopic scales. Kinetic control of nucleation and growth is crucial, with amorphous precursors transforming into crystalline intermediates. Surface adsorbed macromolecules and surfactants influence crystal texture and composition. Mesoscale self-assembly of inorganic-organic hybrid nanoparticles can produce stable or transformable structures. Aggregation-mediated crystallization is prominent in solids like iron oxides, cerium oxide, and copper oxides. Surface charge sensitivity and hydrolytic transformation affect nanoparticle aggregation and crystallization. The alignment of primary particles and their aggregation into continuous crystals is influenced by hydrothermal conditions and oriented attachment. Macromolecules can influence crystal habit through selective adsorption, leading to preferential growth inhibition. Soluble macromolecules and surfactants can significantly affect early stages of crystal growth. Aggregation-based pathways of crystal growth are influenced by polymer interactions, leading to textured single crystals. Strong binding interactions between macromolecules and nanocrystals can result in crystals containing significant levels of occluded organic molecules. Mesoscale self-assembly of nanoparticle arrays is influenced by surface-anchored surfactant molecules. Hydrophobic interactions drive assembly, often reversible unless stabilized by interparticle cross-linkers. Surfactant-coated nanoparticles with high shape anisotropy can self-assemble into ordered superstructures. The sensitivity of ordering transitions to interaction potentials between crystal surfaces and surfactant molecules is highlighted by microemulsion-based reaction fields. Polymer-induced nanoparticle assembly involves phase separation of hydrophilic and hydrophobic segments,