We review optical and electronic properties of Si-based nanostructured materials, such as O-dimensional Si nanocrystallites with sizes from 1 nm to 10 nm and 1-dimensional Si nanowires, that are synthesized using laser ablation techniques. Characteristics of clusters consisting of several atoms to hundreds of atoms are also described in order to understand the physical and chemical properties of Si-based nanostructured materials. Si nanocrystallites with sizes below 5 nm widen band gaps arising from the quantum confinement effect. P and Er impurities exhibit novel properties in SiO2 matrices including Si nanocrystallites. Si nanowire can be grown via vapor-liquid-solid mechanism. Quantized conductance and Coulomb blockade are described for the nanowires having interesting quantum properties.