Gehirn (ゲヒルン, "Gehirun") (German: brain) is NERV's predecessor located outside the GeoFront and tasked with research and development of the Evangelion units and the Magi, amongst other things. Branch 3 is located in Germany. Two other branches are located in the USA, and one probably in China. A minor branch is located in Matsushiro, Japan. Many of its facilities and members (including prominently Gendo Ikari, Yui Ikari, Kōzō Fuyutsuki, Kyoko Zeppelin Sohryu, and Ritsuko Akagi) would become NERV personnel later. It was converted into NERV shortly after Naoko Akagi's death and the MAGI were developed and made operational. The main characters would later see a "graveyard" filled with Gehirn's Failed Evangelion Prototypes, of which line of research Unit-00 and later Evangelions would be made.
Although Gehirn is consistently spelled using all-capital letters, it is not an acronym. Many times during the series English words are spelled in all-capital letters as a stylistic choice by the Japanese production team, including words that are obviously not acronyms such as "ADAM" or "SECOND IMPACT". This has unintentionally led to some confusion when words such as "NERV", "SEELE", and "Magi" are spelled with all-capitals, leading to the incorrect assumption that they are acronyms, also referral to the pyramid and inverted pyramid shaped building called Gehirn.