Glosses are fingerprints of the society in which texts were composed, copied, and read. Most importantly, they play a much more significant role than previous research has acknowledged and offer insights about the multilingual and multi-ethnic environment of medieval manuscript and text production the principal texts cannot: they are first-hand testimonies of the close linguistic and cultural connections between Insular Celtic (Old Breton, Old Irish, Old Welsh) and Latin speakers. GLOSSIT researches these contacts combining methods of comparative philology and historical linguistics, digital humanities (handwritten text recognition, network analysis, natural language processing), (cultural) history, and biological computation (applying DNA-sequence alignment methods to glosses).