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In this paper, we investigate photonic nanojets (PNJs) generated from silicon-based cuboids and grating structures. The cuboid structure consists of a base microcuboid and a nanocuboid sitting on top. By tuning the parameters of cuboids and surrounding medium, we show that ultra-narrow PNJs with spot sizes between 82 nm (~ λ /7.8) and 86 nm (~ λ /7.4) can be achieved under a 638 nm TE-polarized light illumination. These results are comparable to the solid immersion resolution limit of λ /7.8 for silicon lenses, but significantly exceeding the half wavelength limit in air. By arranging an array of hybrid-cuboids structures into a grating structure, we show that the PNJ resolution can be pushed beyond the solid immersion limit, reaching λ /8.3 with spot size ~77 nm. This is one of the highest optical resolutions reported to date for a visible light PNJ array generated by a grating and may find applications in sensing and lithography. [ABSTRACT FROM AUTHOR]