The surface plasmon oscillation in gold nanocrystals will be introduced and its enhancement of the absorption, fluorescence and scattering properties will be discussed as a function of shapes. Excited with femtosecond lasers, the electronic oscillation rapidly relaxes into phonon excitation. The lattice oscillation can be detected optically as it modulates the surface plasmon absorption (the color) of the nanocrystals. The dependence of this oscillation on size, shape and interparticle coupling will be discussed