What is this close-up picture? (WotsThat: Horse chestnut surface (macro))

Question

What object is shown in this zoomed-in close-up photo?

MagpieKing · Accepted Answer

Horse chestnut surface (macro). Horse chestnut seeds have a distinctive shiny brown surface with a pale scar called a hilum, which looks almost like someone deliberately painted a thumbprint on each one—and that "thumbprint" is actually where the seed was attached to the fruit inside the spiky shell. The glossy finish comes from a waxy coating that helps the seed stay hydrated, which is why they feel so smooth and pleasant to carry around, making them a favorite collectible for kids and adults alike.

Answer: Horse chestnut surface (macro)

More botanical close-ups