Recent advances in the field of ambient ionization mass spectrometry are presented briefly, with emphasis on the technique of desorption electrospray ionization (DESI). Numerical multiphase fluid dynamics simulations are used to interrogate droplet-surface collision behavior and resultant progeny droplet formation on an ambient surface subject to the conditions typically associated with DESI. Comparison with previously published experimental results confirms that a momentum-transfer event on a wetted surface is sufficient to replicate known progeny droplet properties. The implications of these mechanistic insights for optimizing the analytical utility of this highly simplified and rapid method of chemical analysis are indicated. (C) 2008 Elsevier B. V. All rights reserved.