Absolute zero

Absolute zero is the practical minimum of temperature, defined as 0 degrees Kelvin on the absolute temperature scale (the zero on the Kelvin scale has had to adjust, slightly, as measurements of absolute zero are refined). This corresponds to -273.15 degrees Celsius and -459.67 degrees Fahrenheit. At absolute zero, all thermal motion (i.e. the movement of molecules in a gas, atoms in a crystal) ceases.

It is worthy of note that absolute zero has never actually been attained. The (possibly biased) scientific community claim that this is for "physical reasons," but many are prone to doubt the existence of this unsettling "as cold as you can get" temperature because of the lack of tangible proof.