It’s a diatom!
To be more precise, these are photos of diatoms beautifully arranged on microscope slides, from the California Academy of Sciences Diatom Collection.
Diatoms are a major group of algae, one of the most common types of phytoplankton. Most of these delicate organisms are microscopic, and only have one cell, but they are distinguished by the remarkable hydrated silicon dioxide cell walls. The chemical composition of these is much like that of the mineraloid we call opal. Thus one can say these algae cells are encased in miniature translucent opal houses, with valves that allow nutrient exchange with the environment, as well as waste excretion.
The shapes of these tiny opalesque diatoms range widely. The California Academy of Sciences boasts a diatom collection they have used to create microscopic arrangements that showcase the astonishing diversity and beauty of these incredibly tiny algae masterpieces.
I’ve shared three below, but make sure to visit Flickr to see the whole album.