Molecular crystals are a type of crystal structure composed of discrete molecules held together by weak intermolecular forces such as van der Waals forces or hydrogen bonding. These crystals are distinct from other types of crystals, such as metallic or covalent crystals, which are held together by different types of bonding. Molecular crystals exhibit unique properties due to the individual nature of the molecules within the crystal lattice. They can have a wide range of physical properties, such as high thermal conductivity, nonlinear optical properties, and high mechanical strength. Research in molecular crystals involves studying their structure, properties, and potential applications in fields such as pharmaceuticals, materials science, and electronics. This research often involves techniques such as X-ray crystallography, spectroscopy, and computational modeling to understand the interactions between molecules within the crystal lattice.