This chapter contextualizes the methodological landscape of formal linguistic heritage language studies, with an emphasis on emerging, innovative trends using online methods (e.g., eye-tracking, EEG/ERP) and statistical methods modeling the dynamic relationship between outcome measures and extra-linguistic factors. Section 22.1 reviews methodological challenges related to testing heritage speaker (HS) knowledge (e.g., modality of testing, issues pertaining to baselines) as well as the history of offline experimentation that typically compares HSs to monolingual baselines, other more balanced bilinguals, and L2 speakers. Section 22.2 considers recent trends in empirical studies adopting online methods contributing both complementary evidence to the considerably larger offline data dominating the field as well as some challenges for claims made on the basis of offline data alone. Section 22.3 unpacks the emerging trend focusing on the continuum of differences within HSs themselves, attempting to quantify, reveal, and understand correlations of individual experiences (using a variety of regression 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 HL grammars develop and end up the way they do.