Finally, the use of scale can be a very effective method for achieving a good visual balance in your layout. By making some elements larger than others, a sense of order and hierarchy will emerge. This helps create a comfortable layout because the viewer will automatically look at the larger elements within the layout first, progressing through to the smaller elements as they read.
Conveying the big picture is always important. While all the elements may connect, the big picture may say it all in one. This idea too, helps the designer control the end users focus. I also like the idea of harmony mentioned, while making small elements zoom into the large picture. This can be helpful in puzzled pictures, or connecting wardrobe for clothing stores, and much more.