Are Axions Really the Dark Matter of the Universe?

The search for dark matter is a very well-defined, exciting frontier. I think to me the most profound problem that's on the borders of boundaries of physics is the question of how mind emerges from matter. Self-reproducing machines would work more like biological development and could be used in terraforming planets or building computers the size of mountains. And then another one I'll mention is kind of expanding our sensorium.