Greg Dunn is one of those people bringing back the art of scientific images. He's a neuroscientist working on his doctorate at UPenn, and paints neurons in the Asian sumi-e style on the side. His works are so free...and yet so incredibly, meticulously, thought out. It's pure elegance.
Glomerulus, commissioned by the University of Pennsylvania
Synaptogenesis (the new Creation of Adam, anyone?)
Retina I (probably my favorite)