The laser fluence is one of the most important parameters. Indeed, the ejection of metal particles from the target requires a minimum power (or fluence). The mean size of the nanoparticles has been found generally to increase with increasing laser fluence and is generally smallest for fluencies not too far above the laser breakdown threshold. Besides the laser fluence, the number of laser shots (i.e. the time spent during laser vaporization) influences the concentration and the morphology of metal particles released in a liquid. For longer times under the laser beam the metal particle concentration is expected to increase, but it can saturate due to light absorption in the colloid highly concentrated in metal particles.