For prosody to be helpful to learn grammar, infants need to process it early in development. When do infants first show sensitivity to prosody and how do they use it to learn grammar? Infants encounter speech prosody in utero. Fetuses already learn from this information, as newborns show differential activation to prosodic patterns found in the language(s) heard during pregnancy and can use prosodic information to process accelerated speech. At 8 months, bilingual infants use phrasal prosody to discriminate the grammars of their two languages. Children can also use subtle prosodic cues to identify meaning. From 3 years, they can use the pitch accent that marks syntactic focus to correctly interpret utterances.