ANNE WESTON, LONDON RESEARCH INSTITUTE, CANCER RESEARCH UK
This diatom frustule is a type of phytoplankton. The organisms are encased inside hard cell walls, and come in a variety of shapes, pores and ridges. These features are used to determine their genera and species.
This diatom is 80 microns in diameter and just happens to look a lot like the universal symbol for radioactivity.