The Panino al Lampredotto is a sandwich built around one cut of offal and a pot of its own broth, and the defining move is the dunk. The lampredotto is the abomasum, the cow's fourth stomach, simmered for hours with tomato, onion, celery, parsley, and aromatics until it is tender enough to slice. It is piled into a plain semelle roll, and then the top of that roll, often the whole thing, is plunged into the simmering broth so the bread comes out saturated and the sandwich is eaten at the edge of structural collapse. This is street food in the most literal sense: bought from a lampredottaio at a cart, dressed in seconds, eaten standing at the kerb with the broth running to the wrist.
The craft is the pot and the two sauces, and the stand lives or dies on the pot. The cooking liquor is the seasoning for everything, so the bread carries it through every bite once it has been dipped, which is why a thin or stale roll is useless and a fresh semelle with a real crumb is essential. The sliced tripe is dressed at the counter with salsa verde, the sharp parsley, caper, anchovy, and garlic sauce that cuts straight through the richness, or with a fierce salsa piccante for those who want heat instead. Salt and pepper are worked in to order. The roll is left plain on purpose, because the offal and the broth are the whole argument and a flavoured bread would only get in their way.
The variations are narrow and entirely Florentine, and each is its own preparation rather than a footnote here. The fully soaked reading, where both halves go into the pot, is the lampredotto bagnato. The same roll dressed only with salsa verde and the same roll dressed with salsa piccante are each their own balance. The plated trippa alla fiorentina and the bollito roll share the offal-and-broth logic from a different angle. Each of those is the same fourth-stomach idea argued differently, and each deserves its own article rather than being crowded in here.