The project studies how the vowel system of so-called "Classical Latin" (CL) evolved into the vowel system of the Romance languages from a diachronic, diatopic, and sociolinguistic perspective (the former system was based on distinctions of vowel quantity, while the latter is mostly based on quality oppositions). To this end, the research considers two different kinds of evidence: metalinguistic testimonies in Latin grammarians ("the indirect sources"), and the instances of the spelling variation involving <e> vs. <i> and <o> vs. <u> in Latin inscriptions (the "direct sources"), which represent the main focus of the research. More precisely, the qualitative, quantitative (and statistical) study of these kinds of "misspellings" in a sociolinguistically-relevant corpus of several thousand inscriptions from Rome (and Italy) aims to address four main research questions: 1) the interpretation of the instances of <e> for (short) /i/ that appear in inscriptions of the 3rd cent. BCE, 2) the relative chronology of the vowel mergers that occurred in most of the Romance languages (/i, eː/ > /e/ and /u, oː/ > /o/), with special reference to the Latin of Rome, 3) the interaction between vowel confusions (<e>/<i> and <o>/<u>) and lexical stress, and 4) the sociolinguistic dynamics that emphasised the reshaping of the CL vowel system into the vowel system of Romance. Moreover,  the project also aims at clarifying the "dialectal position" of Rome regarding developments in the vowel system in the transition from Latin to Romance.