It irritates me a bit that the headline for the negative temperatures article contradicts the article itself:
Headline: 'Atoms Reach Record Temperature, Colder than Absolute Zero'

Article: '"The inverted Boltzmann distribution is the hallmark of negative absolute temperature, and this is what we have achieved," said researcher Ulrich Schneider, a physicist at the University of Munich in Germany. "Yet the gas is not colder than zero kelvin, but hotter. It is even hotter than at any positive temperature — the temperature scale simply does not end at infinity, but jumps to negative values instead."'