Built-in bunk beds is a great idea to preserve space. The built-in book shelves also help to create more storage for toys, books and etc. The first step of the ladder has been eliminated in order to add under bed storage/trundle.
How To Build A Treehouse ? This Tree House Design Ideas For Adult and Kids, Simple and easy. can also be used as a place (to live in), Amazing Tiny treehouse kids, Architecture Modern Luxury treehouse interior cozy Backyard Small treehouse masters