The article explores the use of the moiré effect to engineer topological defects in nematic liquid crystals (LCs), enabling versatile design and manipulation of these defects for various applications. By rotating two substrates with periodic surface anchoring patterns, the researchers observe a rich variety of tunable topological defects, including straight lines, helical-like curves, defect networks, and loops. These defects can guide the three-dimensional self-assembly of colloids and influence defect behavior through mechanisms like jamming. The study demonstrates that nematic moiré cells can generate arbitrary shapes via defect regions, offering a simple method to design and tune mesoscopic structures in LCs. This approach has potential applications in defect-directed self-assembly, material transport, micro-reactors, photonic devices, and anti-counterfeiting materials. Nematic LCs consist of rod-like molecules that self-assemble into mesoscopic structures with long-range orientational order. Topological defects, which arise from local frustration in this order, can segregate foreign molecules and particles, enabling applications in directed self-assembly, photonic devices, biosensing, and material transport. Existing methods for defect manipulation, such as magnetic and electric fields, optical control, and patterned substrates, are limited by the intrinsic symmetry of the system. The moiré effect, inspired by twistronics, offers a new method to manipulate defect structures by rotating one surface relative to another, generating moiré patterns with emerging periodicities. The researchers demonstrate that nematic moiré patterns can manipulate the mesoscopic director field and topological defects in nematic cells, termed "nematic moiré patterns." These patterns can generate a variety of periodic disclination structures, including straight lines, helical-like curves, defect networks, and loops. The 3D topological structures are modeled using continuum simulations and confirmed by confocal microscope experiments. The geometry of these structures is sensitive to twist angles and cell gaps, revealing both low- and high-frequency modes of the geometric moiré. The optical patterns from nematic moirés exhibit grain- and ring-like features, distinct from isotropic moiré patterns. The study further shows that nematic moiré cells can guide 3D self-assembly and nucleation of colloidal structures. When a colloidal particle-laden defect loop undergoes shrinkage, the particles can prevent self-annihilation through jamming. The researchers also demonstrate that certain nematic moiré patterns can engender pixelated shapes represented by defect regions, offering a versatile platform for studying the interplay of topology, geometry, and ordering in LCs and other soft materials. The article highlights the potential of nematic moiré patterns in applications such as anti-counterfeiting materials, photonic devices, and responsive materials. The moiré effect enables precise control over defect structures, allowing for inverse design of mesoscopic structures. The study also explores the response of nematic moirThe article explores the use of the moiré effect to engineer topological defects in nematic liquid crystals (LCs), enabling versatile design and manipulation of these defects for various applications. By rotating two substrates with periodic surface anchoring patterns, the researchers observe a rich variety of tunable topological defects, including straight lines, helical-like curves, defect networks, and loops. These defects can guide the three-dimensional self-assembly of colloids and influence defect behavior through mechanisms like jamming. The study demonstrates that nematic moiré cells can generate arbitrary shapes via defect regions, offering a simple method to design and tune mesoscopic structures in LCs. This approach has potential applications in defect-directed self-assembly, material transport, micro-reactors, photonic devices, and anti-counterfeiting materials. Nematic LCs consist of rod-like molecules that self-assemble into mesoscopic structures with long-range orientational order. Topological defects, which arise from local frustration in this order, can segregate foreign molecules and particles, enabling applications in directed self-assembly, photonic devices, biosensing, and material transport. Existing methods for defect manipulation, such as magnetic and electric fields, optical control, and patterned substrates, are limited by the intrinsic symmetry of the system. The moiré effect, inspired by twistronics, offers a new method to manipulate defect structures by rotating one surface relative to another, generating moiré patterns with emerging periodicities. The researchers demonstrate that nematic moiré patterns can manipulate the mesoscopic director field and topological defects in nematic cells, termed "nematic moiré patterns." These patterns can generate a variety of periodic disclination structures, including straight lines, helical-like curves, defect networks, and loops. The 3D topological structures are modeled using continuum simulations and confirmed by confocal microscope experiments. The geometry of these structures is sensitive to twist angles and cell gaps, revealing both low- and high-frequency modes of the geometric moiré. The optical patterns from nematic moirés exhibit grain- and ring-like features, distinct from isotropic moiré patterns. The study further shows that nematic moiré cells can guide 3D self-assembly and nucleation of colloidal structures. When a colloidal particle-laden defect loop undergoes shrinkage, the particles can prevent self-annihilation through jamming. The researchers also demonstrate that certain nematic moiré patterns can engender pixelated shapes represented by defect regions, offering a versatile platform for studying the interplay of topology, geometry, and ordering in LCs and other soft materials. The article highlights the potential of nematic moiré patterns in applications such as anti-counterfeiting materials, photonic devices, and responsive materials. The moiré effect enables precise control over defect structures, allowing for inverse design of mesoscopic structures. The study also explores the response of nematic moir