As the size of material is reduced to the nanometer length scale, its optical, catalytic and ultrafast dynamical properties greatly change and become sensitive to changes is size or shape. Gold nanorods are over a million times more fluorescent than the metal or the nanospheres. Platinum tetrahedra nanoparticles are more catalytically active than nano-cubes. Other properties that we studied are those of processes occurring on the femto-to-picosecond time scale e.g. electron-hole dynamics in quantum dots and wells in semiconductor nanoparticles, size and shape dependence of electron-phonon relaxation times in gold nanoparticles, and the dynamics of pulsed laser photothermal melting or fragmentation of gold nanorods.