We investigated the physical and chemical changes induced in soot aggregates exposed to laser radiation using a scanning mobility particle sizer, a transmission electron microscope, and a scanning transmission x-ray microscope to perform near edge x-ray absorption fine structure spectroscopy.  Laser-induced nanoparticle production was observed at fluences above 0.12 J/cm2 at 532 nm and 0.22 J/cm2 at 1064 nm.  Our results indicate that new particle formation proceeds via (1) vaporization of small carbon clusters by thermal or photolytic mechanisms, followed by homogeneous nucleation, (2) heterogeneous nucleation of vaporized carbon clusters onto material ablated from primary particles, or (3) both processes.