Nanoimprint lithography (NIL) is a non-conventional lithographic technique for high-precision, high-throughput patterning of polymer nanostructures at low cost. Unlike traditional lithography, which uses photons or electrons to modify resist properties, NIL uses mechanical deformation of the resist to achieve resolutions beyond those of conventional techniques. This review discusses the principles of NIL, focusing on material requirements for molds, surface properties, and resist materials for successful nanostructure replication. NIL is highly efficient due to parallel printing and simple equipment, enabling low-cost processes. A variation, step-and-flash imprint lithography (SFIL), uses a transparent mold and UV-curable precursor, allowing room-temperature processing. NIL has been recognized as a key technology for sub-50 nm lithography and is used in various applications, including electronics, photonics, magnetic devices, and biology. Mold materials must be hard and durable, with high mechanical strength to preserve nanoscale features. Common materials include silicon, silicon dioxide, silicon nitride, and metals. Mold fabrication involves lithography, etching, and surface treatments to ensure proper release and pattern fidelity. Flexible fluoropolymer molds, such as Teflon AF 2400 and ETFE, offer durability and conformal contact with substrates. Resists must be deformable under pressure, have sufficient mechanical strength, and good mold-release properties. Thermal plastic resists are used at temperatures above their glass transition temperature (Tg) to achieve viscous flow. UV-curable resists are preferred for room-temperature processing and offer good etch resistance. Recent developments include siloxane copolymers, fast thermally curable resists, and UV-curable resists with high etch resistance and low shrinkage. These materials enable high-resolution patterning, with applications in electronics, photonics, and biotechnology. NIL's ability to create functional device structures in various polymers makes it a versatile technology for advanced nanoscale applications.Nanoimprint lithography (NIL) is a non-conventional lithographic technique for high-precision, high-throughput patterning of polymer nanostructures at low cost. Unlike traditional lithography, which uses photons or electrons to modify resist properties, NIL uses mechanical deformation of the resist to achieve resolutions beyond those of conventional techniques. This review discusses the principles of NIL, focusing on material requirements for molds, surface properties, and resist materials for successful nanostructure replication. NIL is highly efficient due to parallel printing and simple equipment, enabling low-cost processes. A variation, step-and-flash imprint lithography (SFIL), uses a transparent mold and UV-curable precursor, allowing room-temperature processing. NIL has been recognized as a key technology for sub-50 nm lithography and is used in various applications, including electronics, photonics, magnetic devices, and biology. Mold materials must be hard and durable, with high mechanical strength to preserve nanoscale features. Common materials include silicon, silicon dioxide, silicon nitride, and metals. Mold fabrication involves lithography, etching, and surface treatments to ensure proper release and pattern fidelity. Flexible fluoropolymer molds, such as Teflon AF 2400 and ETFE, offer durability and conformal contact with substrates. Resists must be deformable under pressure, have sufficient mechanical strength, and good mold-release properties. Thermal plastic resists are used at temperatures above their glass transition temperature (Tg) to achieve viscous flow. UV-curable resists are preferred for room-temperature processing and offer good etch resistance. Recent developments include siloxane copolymers, fast thermally curable resists, and UV-curable resists with high etch resistance and low shrinkage. These materials enable high-resolution patterning, with applications in electronics, photonics, and biotechnology. NIL's ability to create functional device structures in various polymers makes it a versatile technology for advanced nanoscale applications.