One non-obvious, but extremely useful, feature in tmux is copy-pasting text between panes. This also allows you to scroll back in a tmux sessoin. We'll cover how to use copy and paste in tmux using C-b [ and C-b ], for both emacs- and vim-style keybindings.
Get into the command mode:
C-b :
Type:
set-window-option mode-keys emacs
Copy & paste:
#enter copy mode: C-b [ # select text: C + space # copy C-w # paste: C-b ]