For as long as humankind has existed, there have been weapons, designed to kill and to protect. Over many millennia, they have taken on leading roles in major battles, helping to build empires and destroy civilizations. This is a look at some of the most important and innovative weapons, from slings and arrows to nuclear bombs to biological warfare. Through unique experiments run by weapons specialists, explore how and why these weapons work and the role each one has played in shaping the world we know today.