For vim there is a filesystem explorer called NERDtree: https://github.com/scrooloose/nerdtree
Surely an alternative or superior package exists for Emacs?
Who needs any tree, when you have the mighty ido-mode . If you can train your mind to find the files, rather than just your eyes whilst visually finding it, you will win. NO need to tell me how biology works, i don't care :-) you get the point.