“The Chimeric intron, which has been demonstrated to significantly increase transgene expression, is included in a variety of the mammalian expression vectors” – Almond, By Brian. “Promega ENotes – Applications.” Promega Corporation – Precision Design for Life.

It seems like a chimeric intron choice is works well as a genetic factor for increasing genetic expression, but my question is how to introns work in general to enhance expression and what makes the Chimeric Intron special?