Until we come up with a full-on invisibility cloak, we're just going to have to settle for making objects less visible in a few specific wavelengths, or alternatively, making them look like something that they're not. BAE's Adaptiv armor system can disguise vehicles in the infrared, turning them into cars, cows, or nothing at all.
Viewing something in infrared wavelengths is analogous to looking at a heat map of it, where colder surfaces are darker and hotter surfaces are lighter. This is why IR scopes are used all the time in combat environments: they work during the day and at night, and you can use them to see warm objects hiding under cooler cover. The only caveat is that if an object is the same temperature as its surroundings, you won't be able to make it out, no matter what it looks like.
BAE Systems has taken advantage the temperature sensing capabilities of infrared systems and created an armor made out of hexagonal "temperature pixels" that can dynamically adjust their heat emissions. You can see these pixels in the pic above, and up close, they look like this:
Using an array of cameras on one side of a vehicle, the pixel array on the opposite side can be instantly commanded to adjust their temperatures to match whatever the camera sees, effectively causing the vehicle to seem to vanish into whatever's behind it when viewed through an infrared scope:
This works even if the vehicle (whether it's a tank, a helicopter, or a ship) is moving, and the pixels can also be programmed to display false patterns, making tanks look like cars or helicopters look like a flock of birds or something. And this IR spoofing isn't just designed to fool human observers: if a heat-seeking missile has no heat signature to seek, it probably won't have much luck hitting whatever it's been aimed at.
There's a video of the armor in action on BAE's website, and it's crazy: entire tanks seem to simply melt away into cars or nothing at all in the infrared. Watch it here, and look for the Adaptiv system to be deployed within just a few years.