When in a sushi restaurant in Japan, you’re likely to see cuts of tuna belly in maki rolls or on their own as sashimi. However, walk through a fish market or grocery store, and you’ll see a very different part of the tuna gazing at you: its eyeballs.

Japanese chefs cook the fleshy, tennis ball–sized eyeballs as appetizers or bar snacks. The eye consists of a hard exterior, known as the sclera, which holds the lens, the iris, and gelatinous fluid. When cooked, the sclera is usually too chewy to eat, but the inner contents of the eye become soft, and can be easily sucked out like bone marrow. Chefs often lightly braise eyeballs in a mixture of soy sauce and mirin or sautée them with sesame oil and ginger. The eyeballs themselves are rather bland—most tasters liken them to squid, mussels, or or hard-boiled egg.

Today, tuna eyeballs can usually be found in Japan’s izakayas, casual, after-work pubs that dispense hors d’oeuvres and drinks. The cooked eyeballs are served one or two at a time, alongside other dishes. If you’re lucky, you may even be able to pair them with a shot of “tuna’s tears,” a rare drink made with soju and raw tuna lens.