Tmux 1.8 introduced a great feature, zoom. Zoom expands the current pane to temporarily fill whole screen. It's helpful when you want to focus or read long lines of code.
The long way to this function is
resize-pane -Z -t target-pane in the Tmux bar.
By default it is also mapped to
prefix + z.
A cool alternative is to map
Down to toggle the zoom. That's how it works in the Hashrocket Dotmatrix:
# tmux.conf unbind Up; bind Up resize-pane -Z; unbind Down; bind Down resize-pane -Z
h/t Chris ErinTweet