You've already learned that if you're using a selection tool (Lasso, Rectangular Marquee, etc.) and you need to add an additional area to your currently selected area, you can hold the Shift key, then any selection you draw with one of those tools will be added. But what if you have a selection and instead you want to create a new selection that will intersect with your existing selection to create an entirely new selection (Whew! That sounds complicated just explaining it)? Here's how: Draw your first selection, then up in the Options Bar you'll find four icons for various selection options. The fourth icon is Intersect with Selection. Click on it, then draw another selection that overlaps your existing selection and all will become clear (grasshopper).