Plutonium is a household word thanks to the nuclear age. From the atom bomb to pop sci fi and from ICBMs to images of Chernobyl I think it's safe to say that pretty much everyone is familiar with the dangers - and fascination - of radiation. Asides from the odd natural atom or two, plutonium was the first metal to be made in a laboratory and most of its intentional production since that time has gone into making either electricity or warheads.

Even though a sand grain-sized piece of plutonium inside a cube such as this would be essentially harmless the availability of this metal to the public is precisely zero; not just because it's radioactive and has no commercial applications but also because if you were to gather enough of it to make a twenty pound ball of it you'd have on your hands your very own nuke. Movie villains and ordinary terrorists would love nothing more than to have such an opportunity!