We examine the collective behavior of two-dimensional nonlinear superconducting metamaterials using a non-contact spatially resolved imaging technique. The metamaterial is made up of sub-wavelength nonlinear microwave oscillators in a strongly coupled 27×27 planar array of radio-frequency Superconducting QUantum Interference Devices (rf-SQUIDs). By using low-temperature laser scanning microscopy we image microwave currents in the driven SQUIDs while in non-radiating dark modes and identify the clustering and uniformity of like-oscillating meta-atoms. We follow the rearrangement of coherent patterns due to meta-atom resonant frequency tuning as a function of external dc and rf magnetic flux bias. We find that the rf current distribution across the SQUID array at zero dc flux and small rf flux reveals a low degree of coherence. By contrast, the spatial coherence improves dramatically upon increasing of rf flux amplitude, in agreement with simulation.Planar arrays of deep sub-wavelength dimension superconducting (SC) resonators have recently gained increasing attention due to their potential use as nonlinear metamaterials, i.e., engineered media whose electromagnetic response can differ dramatically from natural materials. Arrays of coupled SC resonators can be used for controllable routing and manipulating electromagnetic wave propagation in the range from radio-frequency (rf) 1,2 through the THz 3,4 domain. Demonstrated effects include electromagnetically 5 and self-induced broadband transparency, 6 negative magnetic permeability, 7 polarization rotation, 8 Fano resonance, 9 and multi-stable states. 10 Extensive progress on the development and applications of SC metamaterials has been achieved. 2,[11][12][13][14][15][16][17][18][19][20] It has been shown that such SC structures have significant advantages over their normal-metal counterparts allowing reduced losses by several orders of magnitude, shrinking the size of artificial meta-atoms, and achieving tunable frequency of operation by means of macroscopic quantum phenomena. 16,20 Traditional SC metamaterials are composed of ultracompact, self-resonating spirals and split-ring resonators (SRR) of different design. 1,15,16,18,21 Potentially, these structures could be used for switching, 5,10,22 as well as for tuning, by virtue of the dynamic range of well controllable manipulation of their resonances with external stimuli. 23,24 There has been great interest in using radio-frequency Superconducting QUantum Interference Devices: rf-SQUIDs as meta-atoms. 2,7,11,12,16,19,20,22,25,26 Contrary to the SRR and SC spiral, the rf-SQUID incorporates an extremely tunable nonlinear inductor, arising from the Josephson effect, when a Josephson junction is incorporated into a SC loop. The loop geometry adds the macroscopic quantum property of flux quantization, which in turn allows one to conveniently control the Josephson inductance through the magnetic flux applied to the loop. 27 The benefits of the rf-SQUID system were originally presented theoretically in the context of a...