Log Book

The Log book appears in all the Prime series. Samus's log book holds all the information she has scanned through out the game. On Metroid Prime 2: Echoes and Metroid Prime 3: Corruption if Samus gets 100% scan on the log book it reveals a hidden ending at the end of the game. The log book hold data like:

Pirate Data Lore Creatures Research

By finding all of these through out the series you unlock Image Gallerys which can be accesed via the main menu.