It recently came up that there exists an universal Turing machine with two states and three symbols. This is the smallest universal Turing machine known so far; note that smaller Turing machines (with 2 states and 2 symbols) cannot exist.

The problem of finding such a Turing Machine is rather old, but only about an year ago Stephen Wolfram announced a 25,000$ prize for the person who would prove that such a machine is universal. The prize was won by Alex Smith an undergraduate student from UK.

I think that the result it's rather nice. I am curious to see if this small universal Turing machine is also a fast simulator (well, I should read the proof carefully to see this ...). From another point of view, I am curious to see what impact will have this result in the nowadays theoretical computer science; I think that it should be received as an important result, but, however, not as a major breakthrough. It was claimed that such a result may help in finding small universal bio-inspired models: it may be true, since most of the universality results for such models are based on simulations of the Turing machine. However, I think that we won't find a really efficient universal bio-inspired model as long as we don't prove directly an universality result for such a system (or at least simulate a similar model, not a Turing machine).