Before Explosives, the firing rate and fire power of both rifles and artillery were hindered by the nature of their projectiles: black powder (which when fired created a conspicuous black cloud) and solid iron balls. Explosives revolutionized warfare with smokeless powder and TNT. TNT evolved from nitroglycerin, a highly unstable nitrate that in liquid form can explode merely when shaken. Scientists discovered nitroglycerin could be mixed with an absorbent material or "dope," and the combination could be formed and shaped, most commonly into dynamite, but also into explosive shells and land mines.