This chapter contextualizes the methodological landscape of formal linguistic heritage language studies, with a special emphasis on emerging, innovative trends. The chapter is divided in three parts. Part 1 reviews methodological challenges related to testing heritage speaker knowledge (e.g., modality of testing, issues pertaining to baselines) as well as the history of offline behavioral experimentation that typically compares heritage speakers to monolingual baselines (Montrul 2008, 2016; Polinsky, 2018). We will seek to take stock of what has been robustly studied to date versus where there is welcomed room for further investigation in the near future (e.g. the imbalance between heritage speaker developmental studies in young and older aged children and adolescents versus the highly studied case of competence outcomes in (young) adult ultimate attainment, e.g. Kupisch & Rothman, 2016). Part 2 considers recent trends in heritage language empirical studies adopting online methods (e.g., Villegas, 2014; Kim, Montrul & Yoon, 2015; Jacob, Şafak, Demir, Kırkıcı, 2018), contributing both complementary evidence to the considerably larger behavioral data base that dominates the field as well as some challenges for claims made on this basis of behavioral data alone. Part 3 unpacks the emerging trend focusing on the continuum of differences within heritage speakers themselves, attempting to quantify, reveal and understand correlations of individual experiences (using regression statistical analyses) with access to and engagement with input as well as opportunities for converting input to intake that might shed light on how and why individual grammars take the developmental path and end state they do (Bayram et al., 2017; Lloyd-Smith et al., under review).