Microplasmas are usually sustained inside micro-cavities of typical size in the range of 10-1000 μm.The aspect (length-to-width/diameter) ratios of such microplasmas are in the 1∶1 to 20∶1 ranges,and the electron density is typically ~1011-1015 cm-3.To the best of our knowledge,when the discharge size is further reduced down to smaller than 10 μm,rare reports has been found yet.Eden and Park predicted that such microplasmas will show intriguing characteristics,including the breakdown of quasineutrality and the similarity to a supercritical liquid.