Boiling, a type of two phase heat transfer process, has been widely utilized across various industrial applications. The key performance parameter which determines the heat removal in boiling is the critical heat flux (CHF), i.e., the heat flux at which a liquid is dried out from a hot solid surface. The formation of a vapor film envelopes the heated surface and leads to an uncontrollable temperature rise and subsequent device failure . The maximization of CHF is a complex problem that involves nucleation, boiling, and bubble departure. Moreover, there exists an optimal point where the contact line region (where liquid, vapor, and solid phases meet) is maximal (leading to the highest possible evaporation rate), but not large enough for instabilities to cause a dry-out. In practice, the CHF is ∼ 100W /cm 236 and even with significant efforts involving nano/micro-structured surfaces , CHF in pool boiling experiments improved by factor of 2-3 over its nominal value . Surprisingly, theoretical limit of evaporative cooling is in the order of 10kW /cm 241 . Understanding the bubble nucleation processes from surfaces/defects would shed light on the cause of this deviation.