A ball of corethron via The Microbial Loop (Ice Stories: Dispatches from Polar Scientists)

Crossed polars image of reversely zoned clinopyroxene in high-Mg andesite from Whaleback volcano, near Mt. Shasta, CA; image diameter ca. 2 mm (M. Streck).

Source: Minerals, Inclusions and Volcanic Processes (On the Cutting Edge Project, Science Education Resource Center at Carleton College)

Colorized image of the fresh Carbonyl Iron sample.

Source: Characterizing Metal Oxide Coated Carbonyl Iron Particles using Microscopic Techniques, The Institute of Optics (School of Engineering and Applied Sciences at The University of Rochester).

Diatoms, microscopic beauty.

Source (Midlands Technical College)

Murine myoblasts, C2C12 cells.

Source: Differentiated murine myoblasts, University of Massachusetts Amherst.

A fixed PTK (marsupial kidney cell line) cell in mitosis. The condensed chromosomes are stained with Hoechst stain and are shown in blue, while microtubules are labelled with an antibody to tubulin and are shown in red.

Image by Eric Workman and Jim Powers.

Source (Indiana University)