Also called barbina in Tuscany, this is a very thin kind of tagliatelle gathered into nest-shaped bundles.

La minestra di capellini l’è la barbina. L’è quella minestra fatta con quegli spaghettini sottili sottili sottili. I capellini.” (In Tuscan Dialect: “The first course with cappellini is barbina, that dish made with those thin thin thin spaghettini. Capellini.”): T. Poggi Salani, N. Binazzi ed altri, Vocabolario del Fiorentino Contemporaneo, Accademia della Crusca (Contemporary Florentine Dictionary: Crusca Academy): http://www.accademiadellacrusca.it/it/scaffali-digitali/vocabolario-fiorentino). Pastificio Fabbri also produces cappellini, not in nests but as long pasta, like spaghetti.

Ideal with 

Barba is traditionally eaten in broth, also by breaking up the dry bundles with your hands before throwing them into the pot.