A drop of ferrofluid

This is a small portion of one of the best known, and most visually striking images created by Felice Frankel, Senior Research Fellow at Harvard's Initiative in Innovative Computing. What appears to be a work of colorful abstract sculpture...

...is actually a photograph of a 3 cm drop of ferrofluid, a suspension of magnetite in oil. As Frankel explains in her book, Envisioning Science - The Design and Craft of The Science Image - the drop of ferrofluid "was placed on a glass slide," beneath which are a yellow Post-it and seven circular magnets. If one looks carefully at the photo, shot using a 105 mm lens, one can see the photographer's reflection in the droplet.