Collapse

Opens and closes its content by its height - or, horizontal, its width.

Accessibility

Closed with no collapsedSize, the root is visibility: hidden, so its content is out of the tab order and the accessibility tree. With a collapsedSize it stays visible.
Nothing moves for a user who asked for less motion.
Use shouldUnmountOnExit for content that should not exist while it is closed.
Accordion builds its panel on Collapse.