  For decades, researchers worldwide have investigated phenomena related to
natural, artificial oil leakages such as oil drop formation within water
bodies, their rise, and oil slick evolution after they breach the water-air
interface. Despite this, the event leading to slick formation -the bursting of
oil drops at the liquid-air interface has remained unnoticed thus far. In this
work, we investigate this and report a counterintuitive jetting reversal that
releases a daughter oil droplet inside the bulk as opposed to the upwards
shooting jets observed in bursting air bubbles. We show that the daughter
droplet size thus produced can be correlated to the bulk liquid properties and
that its formation can be suppressed by increasing the bulk viscosity, by an
overlaying layer of oil or by the addition of microparticles. We further
demonstrate the significance of our results by synthesizing colloidal pickered
droplets and show applications of bursting compound drops in double emulsions
and studies on raindrop impact on a slick. These results could be immensely
transformative for diverse areas, including climatology, oceanic, atmospheric
sciences, colloidal synthesis and drug delivery.
