Nearly everything modern medicine does to control these invisible killers, further optimizes their resistance to our drugs and combat strategies, and hence their proliferation.

FORBES: The Best and Worst of Times: Killer Vegetables, Plunging Markets, Infinite Nature

Fifth-generation aircraft are invisible to radar, have advanced flight and weapons control systems and can cruise at supersonic speeds, officials say.

BBC: India to buy advanced fighter jets from Russia

This invisible network of mutual back-scratching made it difficult for anyone outside the military to control it - or even understand it.

CNN: A Question Of Loyalty