BAE Systems's Adaptiv technology enables objects as big as tanks to completely vanish from view--when seen at night with an infrared sensor, admittedly, but that's still a major advantage. An Adaptiv-outfitted tank can change its thermal signature to look like anything from a big rock to a truck to nothing at all, fading into the background and becoming invisible.
We've seen a few kinds of invisibility before--there's BAE's own e-ink-based concept, as well as ideas ranging from crystals to metamaterials. But Adaptiv simply uses a system of hexagonal panels, a few inches in diameter each, designed to change temperature very quickly. The BBC says it takes about a thousand of these panels to cover a tank, but when it's covered, it can change its thermal signature at will.