Browsing images online can mean spending a great deal of time clicking thumbnails, waiting for the results to open in a new page, then clicking the Back button to try something else.
Power Zoom is a Chrome extension which can simplify this. Once installed, simply hover your mouse cursor over the image, and the larger version is downloaded and displayed as a popup over the current window. The page doesn't change, and to try something else you just move the mouse: no more clicking Back and waiting for everything to reload.
This can be annoying. Do you really want, say, a larger version of the Google logo to be displayed every time you happen to move the mouse over it? Of course this generates extra network traffic, too. Fortunately you can set the extension to work only if you hold down Ctrl, which provides a little more control.
It's also not ideal in every situation. Power Zoom's larger images won't necessarily be displayed at their maximum possible size, so if it's critical you see the most detail then you'll still need to left-click an image as usual.