It's Stefan-Boltzman Law actually, and it relates the amount energy radiated from a body, E, to its temperature, T.
(Note that E is in Watts/m²; and T is in Kelvin (K).)
E = s • T⁴ (s is a constant - the Stefan-Boltzman constant, and is equal to 5.67 x 10-8 Watts m⁻² K⁻⁴)
And, oh! The Law!!!
The law states that the amount of radiation emitted by a body is directly proportional to the the fourth index of its absolute temperature (its temperature measured on the Kelvin scale).