Then we analyze what = 1 means. We define 𝑆 as the supersaturation of the gas at ambient pressure 𝑃 , and 𝑆 = 𝑐 /𝑐 -1, with 𝑐 the saturated solubility at ambient pressure 𝑃 . According to Henry's law, 𝑐 = 𝐻𝑃 and 𝑐 = 𝐻𝑃 , with 𝐻 the coefficient of Henry's law. Thus, we have 𝑆𝑃 = 𝑃 -𝑃 ≈ 0, which means 𝑆 ≈ 0 . This is consistent with the experimental observations that even at low gas supersaturation (𝑆 ≈ 0), a large number of bulk nanobubbles can exist stably. 25 IV. Nanobubble size can be estimated from the rigidity of the compressed amphiphile monolayers.