The new book Imagination Illustrated takes a look at some of Jim Henson’s never-before-seen sketches and work. It was compiled by archivist Karen Falk, who joined The Jim Henson Company back in 1992, and adapts the journal that the Muppets creator kept throughout his career.

This is supplemented with a trove of little-seen visual material, including rare sketches, personal and production photographs, storyboards, doodles, and much more. Brain Pickings notes that it offers a revealing glimpse into Henson’s life and artistic process. Click through to see a selection of images from the book:

Imagination Illustrated