Hint
They are very, very tiny.
Spoiler
They are insect eggs.
It's so cool how stick insect eggs look like little clay pots and have so much variety.
It's a neat thread so here's an archive.today page of a Nitter instance - archive.today.
These insects are masters of disguise—even before hatching - National Geographic
Photo caption...
Photographer Levon Biss specializes in tiny objects in order to make “the invisible visible.” He spent hours cleaning these phasmid eggs with distilled water and one paintbrush hair under a microscope. The eggs in this composite grid of images average about 0.12 inch long.
They remind me of netsuke.
A netsuke (根付, [netsɯ̥ke]) is a miniature sculpture, originating in 17th century Japan. Initially a simply-carved button fastener on the cords of an inrō box, netsuke later developed into ornately sculpted objects of craftsmanship.
I thought it was some pottery work at first glance. This is very neat.