Looks like there's thin white things between the towers (which are substrate, revealed by deep trench RIE and filled in around by SiO2 or something else), which might be the fins of the FETs? Or gates?
AFAIK, feature size refers to the ability to go from "on" to "off" in any given layer, so there might not be any physical regions that actual size, but it's nonetheless required to make devices that small.
Tim