Nanoscale gas bubbles have surprising stability at water/solid surfaces. Herein, we summarize progress made on investigating gases at the water/solid interfaces on the nanometer scale. The gas states include nanobubbles, micropancakes, multiple gas layers and their coexistence; these were investigated from experimental and theoretical aspects. The stability of nanoscale gas bubbles may be attributed to high inner density, as observed in molecular dynamic simulations and theoretical analysis. Moreover, it was found that there were maximal length scales for stable nanobubbles, namely, 100 nm high and a curvature radius of 2 μm.