From top-to-bottom, many geological, geophysical, petrologic/geochemical, and theoretical advancements have been made toward understanding subduction zone processes and dynamics. The term “subduction” was introduced in its modern sense in 1970 and the 1996 AGU Geophysical Monograph “Subduction Top to Bottom” marked a milestone in our understanding by capturing 26 years of early advances. This “Subduction Top to Bottom 2” (ST2B-2) session and a related themed issue in the GSA journal GEOSPHERE (now at more than 60 papers and growing) revisit these issues and re-assess them in light of recent advancements as well as explore new discoveries and advances in subduction zone research. We invite the broadest possible range of contributions, including abstracts considering subduction-related hazards, climate effects, and resources. We encourage presentations regarding processes at modern subduction zones and evidence of ancient subduction yielding insight regarding Earth plate tectonic evolution and processes at depth in modern margins.