The Third Law of Thermodynamics states that it is impossible to cool a system to absolute zero, the temperature at which the movement of particles comes to a halt.
But scientists have gotten pretty close to zero degrees Kelvin (or −459.67 degrees F). In 1999, researchers in Helsinki cooled portions of a piece of rhodium metal to 100 picokelvins, just one tenth of one billionth of a degree above absolute zero. The researchers then presumably dared each other to lick it.