When clear Pyrex glass coffee pots came out after WWII it was quite a show watching the bubbles form when the pot was in direct contact with the hot-plate heater coils.
*http://wins.engr.wisc.edu/teaching/mpfBook/node27.html*<http://wins.engr.wisc.edu/teaching/mpfBook/node27.html> "Vapor may form from a liquid (a) at a vapor-liquid interface away from surfaces, (b) in the bulk of the liquid due to density fluctuations, or (c) at a solid surface with pre-existing vapor or gas pockets. In each situation one can observe the departure from a stable or a metastable state of equilibrium. The first physical situation can occur at a planar interface when the liquid temperature is fractionally increased above the saturation temperature of the vapor at the vapor pressure in the gas or vapor region. Thus, the liquid "evaporates" into the vapor because its temperature is maintained at a temperature minimally higher than its vapor "saturation" temperature at the vapor system pressure. Evaporation is the term commonly used to describe such a situation which can also be described on a microscopic level as the imbalance between molecular fluxes at these two distinctly different temperatures."
