Toggle the browser sidebar separately for each window.  Drag and drop images into the sidebar to add them to the file list, or drop them onto the Highbrow application icon to open a new window with its own image browser.

Copy and move files, rename files and and folders... or just enjoy your favorite photos of your friends at the maximum possible resolution.

Highbrow gets out of the way and displays your photos the way they were meant to be seen: without the clutter of toolbars and buttons, as if you had a collection of snapshots on your desktop.