GustavoG

The entire field is ice. :)
Those are air bubbles inside a cylindrical block of ice.

I simply filled a clean plastic jar of peanut butter with tap water, some two-thirds full, and let it freeze outside.
When it started thawing (as the outside temperature went up) I noticed the beautiful pattern of air bubbles in the ice. I extracted the ice from the jar, set it (rather precariously) on the lid, and shot it in "super macro" mode. No image processing beyond rotating it.