The authors demonstrate that it is possible to transform a supercooled liquid metal at room temperature into a variety of shapes in solids by combined liquid metal deformation and induced crystallization from the supercooling state. The authors discover that both reversible deformation and irreversible deformation can be achieved simultaneously for supercooled liquid gallium in alkaline or acid electrolytes by using electrodes that are non-wetted or wetted with liquid gallium, respectively. Our findings on the simultaneous deformation and solidification offer a novel approach to controlled patterning and solidification of supercooled liquid gallium at room temperature.Controlling the shape of liquid metals is still a big challenge. [1][2][3][4] Giant deformation at room temperature in liquid metals such as gallium and gallium alloys is caused by significant reduction of the surface tension of liquid metals due to the formation of oxide on the liquid metal surface under application of voltage. The giant deformation capability can lead to an enhanced capillary effect in thin tubes, [5] migration of liquid metal droplets on a solid surface, and significant shrinkage of liquid metal footprint area. [6] The liquid metals retain their liquid states for all these deformation phenomena at room temperature. The deformation from a liquid droplet can be reversible, i.e., the liquid metal can return to its initial spherical shape after the voltage is switched off. This reversible deformation capability makes room temperature liquid metal potentially useful for soft robotics, [7][8][9] microfluidic applications, [10][11][12] and stretchable soft electronics. [13][14][15] The supercooling effect is the process by which the temperature of a liquid falls below the freezing point, but there is no transition to its solid state. Various properties of liquids can be changed sharply in the supercooling state, such as the isobaric heat capacity [16] and isothermal compressibility [17] in liquid water. The phase change between solid and liquid have been widely studied in various type of materials by changing temperatures. [18][19][20][21] It has been reported that by using a uniform electric field, the liquid gallium can be deformed into a uniform and flat shape, and then freeze below the melting temperature of gallium, enabling gallium to be used as a reconfigurable optical reflector. [19] Gallium is a rare near-room-temperature liquid metal with many unique properties. Liquid metal gallium possesses remarkable properties, such as high electrical conductivity, high thermal conductivity, high surface tension, extremely low vapor pressure, and low toxicity. The melting point of gallium is 29.8 C, [22] and it can stay in the liquid state (supercooling state), when the temperature is reduced to an extraordinary degree (À28.2 C). [23] Therefore, it is more convenient to manipulate gallium in its supercooled state at room temperature.In this Communication, we propose a method to transform liquid metals from the liquid to the solid state and...