Well, it was -273oC, so that's 0.15K. Some research team in Helsinki, using Rhodium, I believe.
In fact it was even colder than that - 100 picokelvins (10
-10 Kelvin).
Well, you can get negative kelvin temperatures, but I don't think that's what you're looking for 
Otherwise it's easily below 2.7 K since we can achieve temperatures colder than space.
For those of you who know what Kelvin is, and think that Edison must just have said something rubbish, read on...
It is not possible to cool a system to below absolute zero. However, temperature isn't really about how hot something is, but is rather a property of a system. Absolute zero means that the system has reached a minimum value of something called entropy - which is basically a measure of the "messiness" of the system. At the other end of the scale, adding temperature to a system will increase its entropy forever.
Or does it?
Lasers work by adding energy to electrons, causing them to jump to a higher energy level (and then falling back down, releasing light). This is called "population inversion" (or basically, the electrons start gathering together in a different place). When that starts happening - when more electrons are in the higher energy state than in the lower energy state - you start adding energy to the laser but the entropy has decreased! This is expressed by saying that the system has reached a "negative temperature" - which means not that it is colder than absolute zero, but that it is hotter than "infinity".
When your brain has cooled down enough...
This means that the "hottest temperature" a system can reach is just below 0 Kelvin.
This is one of a number of times in physics when there is some sort of symmetry around a particular point. In relativity, it's often said that you can't travel faster than light. In fact this is wrong - what you cannot do is move from a speed slower than light to one that is faster. However, if you were travelling faster than light to begin with, then you can't move to a speed slower than the speed of light. This is why physicists can talk about particles that travel faster than light: the "tachyon" - a particle that crops up in Star Trek to help make it sound fancy - may or may not exist, but if it does it travels faster than light at all times. It also travels backwards in time.
