This study explored the thermal,conditions necessary for the vaporization of superheated perfluorocarbon nanodrops: Droplets C3F8 and C4F10 coated with a homologous series of saturated diacylphosphatidylcholines were formed by condensation of 4 mu m diameter microbubbles. These drop,were stable at room temperature and atmospheric, pressure, but-they vaporized back into microbubbles at higher temperatures. The vaporization transition was measured as a function of-temperature by laser light extincton. We found that C3F8 and C4F10 drops experieneed 90% vaporization at 40 and 75 degrees C, respectively, near the theoretical superheat,limits (80-90% of the critical temperature). We therefore conclude that the metastabilty of these phase change agents arises not from the droplet Laplace pressure altering the boiling point, as previously reported, but from the metastability of the pure superheated fluid to homogeneous nucleation. The rate of C4F10 drop vaporization was quantified at temperatures ranging from 55 to 75 degrees C, and an apparent activation energy barrier was calculated from an Arrhenius plot Interestingly, the activation energy increased linearly with,acyl,chain length from C14 to C20, indicating that lipid interchain cohesion plays an important role in suppressing the vaporization rate. The vaporized drops (mitrobubbles) were found to be, unstable to dissolution at high temperatures, particularly for C14 and C16. However, proper choice of-the fluorocarbon and lipid species provided a nanoemulsion that could undergo at least ten revertible condensation/vaporization cycles. The vaporization properties presented in this study, may facilitate the engineering of tunable phase-shift particles for diagnostic imaging, targeted ding delivery, tissue ablation, and other applications.