This is the first time is visually depicted in the franchise.
A significant post-credits scene shows Marcoh and May finding the research notes; this was notably omitted in some original broadcasts due to time. Episode 33 (2009 Anime) | Fullmetal Alchemist Wiki | Fandom Fullmetal Alchemist: Brotherhood Episode 33
: Adapted from Chapters 64 and 65 of the manga. This is the first time is visually depicted in the franchise