Tmux: how to put 2 open windows side by side?

Question

I opened two windows in a tmux session, how can I place them side by side, as if horizontally divided?

Answer 1

I actually found a way to do this. Suppose the two windows are numbers 1 and 2. Use

join-pane -s 2 -t 1 

This will move the window 2 ^nd as a panel into window 1 ^st . Opposite break-pane command