Actually, most humans can see a bit beyond the fiducial visible band = 0.4--0.7 μm. The actual average range may be more like ∼ 0.380--0.750 μm = 380--750 nm???. But everyone's eye sensitivity (i.e., human eye luminosity function) is a bit different.
The extreme human visible range ≅ 0.310--1.050 μm. To see well beyond the fiducial range = 0.4--0.7 μm requires bright sources, ideal conditions, and for the ultraviolet part to have young eyes. There is NO revelation though---ultraviolet is reported as looking blue-white (see Quorra: What does the ultraviolet color look like?) and infrared just looks deep red (e.g., PP-19). It may NOT be safe to look for very long at intense sources beyond the fiducial range = 0.4--0.7 μm---but yours truly does NOT know.