Layers may be set to become visible or invisible as zooming in or out occurs in a map window (Primary Layers and Map Layers). This allows you to display finer levels of detail as you zoom in on regions in a map window and avoid clutter when displaying the full area. This might include time series icons not appearing for less significant gages, detailed map layers becoming visible, and raster or other images appearing that are not as distinguishable at a coarser zoom level.