Monalisa fully supports Child Theme.
A WordPress child theme is a theme that inherits the functionality of the parent theme. With a child theme, you can make a modification or add additional functionality to the parent theme. A child theme is a safest and easiest way to modify an existing theme, whether you want to make a few tiny changes or extensive changes.
You may read how to create child theme here http://codex.wordpress.org/Child_Themes