Reading a long-form piece on, say, the Peloponnesian War. Thucydides gets mentioned as a primary source. I half-know who he is — historian, Athenian, that's about it — but not enough to understand why the author is citing him specifically over Herodotus. Opening a new tab means I lose the sentence I was in. Skipping it means I read shallower than the text deserves. rabbitholes is a Chrome extension that solves this with a shadow-DOM tooltip. Highlight any text, get an inline explanation from Claude next to your cursor. The host page is untouched — shadow DOM keeps the overlay isolated so it doesn't conflict with the site's styles or scripts. The part I use most: every word in the explanation is itself clickable. Highlight "Thucydides," get an answer that mentions "the Peloponnesian War," click that phrase to go deeper. Each answer also surfaces two suggested rabbit-hole topics — the most interesting threads from where you currently are.…