  We report frozen patterns for the water droplets impacting on a cold
substrate through fast-speed images. These patterns can be manipulated by
several physical parameters (the droplet size, falling height, and substrate
temperature), and the scaling analysis has a remarkable agreement with the
phase diagram. The observed double-concentric toroidal shape is attributed to
the correlation between the impacting dynamics and freezing process, as
confirmed by the spatiotemporal evolution of the droplet temperature, the
identified timescale associated with the morphology and solidification
($t_{inn}\simeq \tau_{sol}$), and the ice front-advection model. These results
for frozen patterns provide insight into the complex interplay of the rapid
impacting hydrodynamics, the transient heat transfer, and the intricate
solidification process.
