Stacked microscopic image of the radiolarian Anthocyrtium hispidum Haeckel (magnification 400x), found in Barbados and aged approximately 32-35 million years (late Eocene – early Oligocene). Radiolarians (Polycystinea) are microplanktonic, open ocean protozoa characterized by a delicate skeleton of opaline silica or strontium sulfate and classed into the phylum Retaria. Specimen prepared by Andreas Drews, image by Picturepest and retrieved from Flickr; image modified by MIC. The cover is published under the Creative Commons Attribution (CC BY) license.