Sample All Layers
Previously called Use All Layers, this setting is found in the options bar of the Clone Stamp, Smudge, Blur, Sharpen, Paint Bucket and Healing Brush tools. It allows the user to select a sample area based on all visible layers not just the contents of the selected layer.
In CS2 the Sample All Layers replaces the Use All Layers name. This setting still resides on the options bar of the tools with which it can be used.
Sample Size, Eyedropper tool