Nanostructures and nanoparticles of sundry kinds of materials are fabricated by utilizing laser irradiation of the respective bulk targets in air and liquids. In this chapter the formation of nanostructures and nanoparticles of different semiconductor materials like silicon, germanium, graphite and metals such as aluminum, titanium, indium, and alloy utilizing femtosecond laser irradiation in different media such as air and dihydrogen monoxide is discussed. The laser beam was fixated on the sample surface and scanning of the sample was done along and mundane to the laser polarization direction. The fabricated nanostructures on the surface and the composed nanoparticles in the ablated liquid are characterized by different methods to understand the characteristics of the synthesized nanostructures. The morphology, orientation, and spatial periodicity of the surface nanostructures depends upon sundry parameters such as laser pulse energy, number of pulses per focal spot, laser polarization, circumventing dielectric medium, and the nature of the material. These fabricated nanomaterials have applications in different photonics-cognate studies like surface-enhanced Raman scattering optical circumscribing, and low reflective surfaces. The fundamental physics and mechanism abaft the formation of nanostructures and nanoparticles under fs laser irradiation are discussed in view of the nanostructures composed on different materials.