  Pressure reduction in liquids may result in vaporization and bubble
formation. This thermodynamic process is termed cavitation. It is commonly
observed in hydraulic machinery, ship propellers, and even in medical therapy
within the human body. While cavitation may be beneficial for the removal of
malign tissue, yet in many cases it is unwanted due to its ability to erode
nearly any material in close contact. Current understanding is that the origin
of heterogeneous cavitation are nucleation sites where stable gas cavities
reside, e.g., on contaminant particles, submerged surfaces or shell stabilized
microscopic bubbles. Here, we present the finding of a so far unreported
nucleation site, namely the atomically smooth interface between two immiscible
liquids. The non-polar liquid of the two has a higher gas solubility and acts
upon pressure reduction as a gas reservoir that accumulates at the interface.
We describe experiments that clearly reveal the formation of cavitation on
non-polar droplets in contact with water and elucidate the working mechanism
that leads to the nucleation of gas pockets through simulations.
