Perhaps one of the biggest unanswered questions we have is "how did life begin?" Scientists have been working in the area of abiogenesis for some time now, beginning with the Miller-Urey work on the early-Earth atmosphere (which I've commented on previously). And there's reasonable agreement that the precursors to life were probably some sort of self-replicating molecule, perhaps a proto-nucleic acid or enzyme (and remember that RNA can act as an enzyme).
Now PZ's written about an interesting paper describing how two researchers 'built' simple catalytic molecules that can self-assemble themselves from even simpler substrates - and used natural selection in the process.
And no, the researchers are not claiming that this is what actually happened way back when, but, as PZ says, "it's more like a proof of concept of the idea". Definitely an area to watch :-)