Menu: Window Show/Hide Channels
F7 shows or hides the Layers palette. Also use it to show or hide the Channels palette if you haven't changed the default grouping of the Layers and Channels palettes. To show Channels if the Layers palette is not open , press F7, and then click on the Channels tab. To hide both the Channels and the Layers palettes, press the F7 key until they both disappear.