While playing through the game, you’ll notice that you slowly (or quite suddenly) unlock images called Chozo Memories, which are collected in the Gallery. Most Chozo Memories are linked to your item-collection rate, meaning you have to grab every item tank in the game to unlock the entire Gallery. It’s rumored that there’s a secret Chozo Memory that can only be viewed once you’ve unlocked the rest of the Gallery. Who really knows, though? Sometimes rumors are just rumors.
Metroid: Samus Returns eGuide Extras