Nanoscale thermal transport is a critical area of research due to the increasing importance of thermal management in nanoscale devices and materials. This review summarizes recent developments in experimental, theoretical, and computational approaches to understanding thermal transport at the nanoscale. Interfaces between materials become increasingly significant at small length scales, and the thermal conductance of solid-solid interfaces has been studied experimentally, though the observed properties often differ from theoretical predictions. Classical molecular dynamics simulations are emerging as a powerful tool for calculating thermal conductance and phonon scattering, enabling a deeper understanding of the interplay between experiment and theory. The thermal transport in nanoscale systems is dominated by phonons, which have a wide range of frequencies and mean-free-paths (mfps). At room temperature, phonons typically have mfps of 1–100 nm, which is comparable to the scale of nanoscale microstructures. This necessitates a deeper understanding of heat transport beyond the continuum level, as traditional analytical theories are insufficient to capture the wave nature of phonons at these scales. Defining temperature in nonequilibrium nanoscale systems remains a fundamental challenge. Recent experimental techniques, such as the 3ω method, time-domain thermoreflectance, and scanning thermal microscopy, have enabled new capabilities for nanoscale thermal metrology. These methods have been used to study thermal conductivity in various nanoscale structures, including carbon nanotubes and superlattices. However, the agreement between experimental results and theoretical predictions is often poor, particularly for semiconductor superlattices. The thermal conductance of model interfaces has been studied extensively, with results showing that the highest thermal conductance for metal/dielectric interfaces is only a factor of 5 larger than the lowest conductance, Pb/diamond. Heat pulse and coherent phonon experiments have provided insights into phonon transmission across interfaces, while molecular-dynamics simulations have been used to study phonon-phonon interactions and thermal transport at the atomic level. The transport theory for nanoscale systems is based on the Boltzmann transport equation (BTE), which describes the transport of electrons and phonons in solids. However, the BTE assumes classical particles and neglects wave interference effects, which are significant at the nanoscale. Quantum mechanical approaches, such as the quantum Boltzmann equation, have been proposed to account for these effects, but they are complex and difficult to solve. The thermal transport in nanoscale structures and devices is influenced by various factors, including grain boundaries, impurities, and the microstructure of the material. Silicon films and devices have been studied extensively, with results showing that phonon scattering on grain boundaries and impurities significantly reduces the thermal conductivity. The thermal conductivity of silicon films is also affected by the thickness of the film and the doping concentration. In conclusion, the study of nanoscale thermal transport is a complex and multidisciplinary field that requires a combination of experimental, theoretical, andNanoscale thermal transport is a critical area of research due to the increasing importance of thermal management in nanoscale devices and materials. This review summarizes recent developments in experimental, theoretical, and computational approaches to understanding thermal transport at the nanoscale. Interfaces between materials become increasingly significant at small length scales, and the thermal conductance of solid-solid interfaces has been studied experimentally, though the observed properties often differ from theoretical predictions. Classical molecular dynamics simulations are emerging as a powerful tool for calculating thermal conductance and phonon scattering, enabling a deeper understanding of the interplay between experiment and theory. The thermal transport in nanoscale systems is dominated by phonons, which have a wide range of frequencies and mean-free-paths (mfps). At room temperature, phonons typically have mfps of 1–100 nm, which is comparable to the scale of nanoscale microstructures. This necessitates a deeper understanding of heat transport beyond the continuum level, as traditional analytical theories are insufficient to capture the wave nature of phonons at these scales. Defining temperature in nonequilibrium nanoscale systems remains a fundamental challenge. Recent experimental techniques, such as the 3ω method, time-domain thermoreflectance, and scanning thermal microscopy, have enabled new capabilities for nanoscale thermal metrology. These methods have been used to study thermal conductivity in various nanoscale structures, including carbon nanotubes and superlattices. However, the agreement between experimental results and theoretical predictions is often poor, particularly for semiconductor superlattices. The thermal conductance of model interfaces has been studied extensively, with results showing that the highest thermal conductance for metal/dielectric interfaces is only a factor of 5 larger than the lowest conductance, Pb/diamond. Heat pulse and coherent phonon experiments have provided insights into phonon transmission across interfaces, while molecular-dynamics simulations have been used to study phonon-phonon interactions and thermal transport at the atomic level. The transport theory for nanoscale systems is based on the Boltzmann transport equation (BTE), which describes the transport of electrons and phonons in solids. However, the BTE assumes classical particles and neglects wave interference effects, which are significant at the nanoscale. Quantum mechanical approaches, such as the quantum Boltzmann equation, have been proposed to account for these effects, but they are complex and difficult to solve. The thermal transport in nanoscale structures and devices is influenced by various factors, including grain boundaries, impurities, and the microstructure of the material. Silicon films and devices have been studied extensively, with results showing that phonon scattering on grain boundaries and impurities significantly reduces the thermal conductivity. The thermal conductivity of silicon films is also affected by the thickness of the film and the doping concentration. In conclusion, the study of nanoscale thermal transport is a complex and multidisciplinary field that requires a combination of experimental, theoretical, and