The processes that lead to material ejection when a solid sample is irradiated near and above the pulsed laser ablation threshold are discussed. Emphasis is placed on the thermal and mechanical mechanisms that occur during pulsed laser irradiation of metals and semiconductors. Distinctions are drawn between ultrafast-pulsed irradiation, which occurs under stress confinement, and shortpulsed irradiation, in which stress is released during the laser pulse. Similarly, the distinctions between the spallation and phase explosion regimes are discussed. Spallation is only possible when the time of the laser heating is shorter than the time needed for mechanical equilibration of the heated volume, while phase explosion can occur for pulses shorter than tens of ns. Nanoparticle formation can occur directly in the plume as the result of the decomposition of ejected liquid layers or a porous foam created by the phase explosion, as well as through condensation of vaporized atoms (enhanced by the presence of an ambient gas).