Nanoscale manipulation of magnetic fields has been a long‐term pursuit in plasmonics and metamaterials, as it can enable a range of appealing optical properties, such as high‐sensitivity circular dichroism, directional scattering, and low‐refractive‐index materials. Inspired by the natural magnetism of aromatic molecules, the cyclic ring cluster of plasmonic nanoparticles (NPs) has been suggested as a promising architecture with induced unnatural magnetism, especially at visible frequencies. However, it remains challenging to assemble plasmonic NPs into complex networks exhibiting strong visible magnetism. Here, a DNA‐origami‐based strategy is introduced to realize molecular self‐assembly of NPs forming complex magnetic architectures, exhibiting emergent properties including anti‐ferromagnetism, purely magnetic‐based Fano resonances, and magnetic surface plasmon polaritons. The basic building block, a gold NP (AuNP) ring consisting of six AuNP seeds, is arranged on a DNA origami frame with nanometer precision. The subsequent hierarchical assembly of the AuNP rings leads to the formation of higher‐order networks of clusters and polymeric chains. Strong emergent plasmonic properties are induced by in situ growth of silver upon the AuNP seeds. This work may facilitate the development of a tunable and scalable DNA‐based strategy for the assembly of optical magnetic circuitry, as well as plasmonic metamaterials with high fidelity.

In this review, it is argued that soft mass migrations, driven and guided by spatially controlled photopolymerization and photochromic isomerization (also called directional plastic deformation or photofluidization of azobenzene materials), offer toolsets for optical engineers to develop various micro/nanophotonic materials and devices that are not readily available with conventional lithographic methods and self‐assembly techniques. In this direction, the two seemingly different concepts of (i) photopolymerization and (ii) photochromic‐isomerization‐driven mass migrations are tied together, and then recent technological advances in these two fields are summarized, including diffractive optical elements (DOEs), electro‐optic DOE devices, colorimetric sensors, biologically inspired optics, plasmonic devices and near‐field studies, and exceptional point optics. This review establishes the technological viability of light‐directed soft mass migration for the overall evolving field of micro/nanophotonics and its research perspectives.

Spontaneous core-hatching process is introduced to double emulsion droplets for implementing further structural tunability and optical responsiveness in colloidal photonic crystals.