Two-dimensional (2D) materials and van der Waals heterostructures have seen rapid development, with new materials enabling truly 2D physics, such as the absence of long-range order, 2D excitons, and commensurate-incommensurate transitions. Novel heterostructure devices, including tunneling transistors, resonant tunneling diodes, and light-emitting diodes, are emerging, leveraging the unique properties of 2D crystals. The family of 2D materials has expanded since graphene's discovery, with each material offering distinct electronic properties. Band gap engineering is achievable by varying the number of layers, and specific 2D physics, such as Kosterlitz-Thouless behavior, is observed. Transition metal dichalcogenides (TMDCs) exhibit diverse electronic behaviors, from insulating to metallic, due to the filling of d-orbitals. Their electronic structure is influenced by inversion symmetry and coordination, leading to piezoelectricity and unique electronic properties. TMDCs show CDW and superconductivity, with complex phase diagrams due to competition between these states. Transport data in TMDCs, combined with electric and magnetic fields, reveal phase transition control and novel phenomena in superconducting phases. 2D systems exhibit unique phase transitions, with quantum critical points at zero temperature. The KT transition allows quasi-long-range order with vortex-antivortex pairs. The electronic properties of semiconducting TMDCs are dominated by excitonic effects, with distinct optical transitions. Phosphorene, a monoelemental 2D material, has high carrier mobility and is used in optoelectronics. Group-IV monochalcogenides, like SnS and GeSe, have semiconducting properties and are suitable for valleytronics. Gallium and indium monochalcogenides have unique band structures and potential for ferromagnetic instability. Hexagonal boron nitride (hBN) is an ideal encapsulating layer due to its high bandgap and resistance to contamination. Oxide layers and other insulators provide new 2D materials with diverse properties, including high thermal conductivity and optoelectronic capabilities. Van der Waals heterostructures are assembled using techniques like wet transfer and "pick and lift," enabling the creation of diverse heterostructures. These structures exhibit clean interfaces and high electron mobility. Self-cleansing mechanisms ensure contamination-free interfaces, while surface reconstruction occurs in materials with similar lattice constants. Capacitive coupling in heterostructures allows for studying quantum capacitance and interaction phenomena. Tunneling devices, such as field-effect tunneling transistors, utilize hBN as a tunneling barrier. Photovoltaic applications benefit from combinations of graphene and TMDCs, enabling efficient carrier separation and high quantum efficiency. Light-emitting diodes and plasmonic devices leverage the unique properties of 2D materials, with plasmon-phonon polaritTwo-dimensional (2D) materials and van der Waals heterostructures have seen rapid development, with new materials enabling truly 2D physics, such as the absence of long-range order, 2D excitons, and commensurate-incommensurate transitions. Novel heterostructure devices, including tunneling transistors, resonant tunneling diodes, and light-emitting diodes, are emerging, leveraging the unique properties of 2D crystals. The family of 2D materials has expanded since graphene's discovery, with each material offering distinct electronic properties. Band gap engineering is achievable by varying the number of layers, and specific 2D physics, such as Kosterlitz-Thouless behavior, is observed. Transition metal dichalcogenides (TMDCs) exhibit diverse electronic behaviors, from insulating to metallic, due to the filling of d-orbitals. Their electronic structure is influenced by inversion symmetry and coordination, leading to piezoelectricity and unique electronic properties. TMDCs show CDW and superconductivity, with complex phase diagrams due to competition between these states. Transport data in TMDCs, combined with electric and magnetic fields, reveal phase transition control and novel phenomena in superconducting phases. 2D systems exhibit unique phase transitions, with quantum critical points at zero temperature. The KT transition allows quasi-long-range order with vortex-antivortex pairs. The electronic properties of semiconducting TMDCs are dominated by excitonic effects, with distinct optical transitions. Phosphorene, a monoelemental 2D material, has high carrier mobility and is used in optoelectronics. Group-IV monochalcogenides, like SnS and GeSe, have semiconducting properties and are suitable for valleytronics. Gallium and indium monochalcogenides have unique band structures and potential for ferromagnetic instability. Hexagonal boron nitride (hBN) is an ideal encapsulating layer due to its high bandgap and resistance to contamination. Oxide layers and other insulators provide new 2D materials with diverse properties, including high thermal conductivity and optoelectronic capabilities. Van der Waals heterostructures are assembled using techniques like wet transfer and "pick and lift," enabling the creation of diverse heterostructures. These structures exhibit clean interfaces and high electron mobility. Self-cleansing mechanisms ensure contamination-free interfaces, while surface reconstruction occurs in materials with similar lattice constants. Capacitive coupling in heterostructures allows for studying quantum capacitance and interaction phenomena. Tunneling devices, such as field-effect tunneling transistors, utilize hBN as a tunneling barrier. Photovoltaic applications benefit from combinations of graphene and TMDCs, enabling efficient carrier separation and high quantum efficiency. Light-emitting diodes and plasmonic devices leverage the unique properties of 2D materials, with plasmon-phonon polarit