Aspect – the grammatical category associated with the internal temporal properties of a situation – is obligatorily marked in the grammar of many languages. Although it is used pervasively, innovative patterns commonly appear in situationsof language contact. Thus, aspect provides an ideal window into the dynamic language patterns that occur in heritage grammars. This chapter reviews six studiesconducted in the context of the Research Unit Emerging Grammars that investigatedynamic patterns in the use of aspect in monolingually-raised speakers of Greek,Russian, and Turkish as well as heritage speakers of each of these languages livingin the US and Germany. Each study uses production and/or comprehension tasks toexplore one or more potential sources of these dynamic patterns, including cross-linguistic influence, verbal morphology and markedness of the aspectual features,formality (formal vs. informal), mode of expression (spoken vs. written), and participant age. The results show several innovative patterns and some differencesin processing in heritage speakers, but largely find that monolingually-raised andheritage speakers produce and process aspect marking in a qualitatively similarway.