HyperDock for Mac lets you take a quick look at the windows you have open in each program when you hover over icons in the Dock. See thumbnails of both open and minimized windows in the same place, and quickly access the programs you need with one click through this app's intuitive and convenient interface.
When you install HyperDock, it will run from the System Preferences menu. To customize your user experience, you can set Preferences for Enabling Window Previews and Activation Delay Time in milliseconds. It's also possible to select whether or not you want to include windows from all display spaces in the thumbnail previews that pop up, and to turn on or off the inclusion of minimized windows. Windows previews can appear in order of creation time or of most recent usage, and you can select or deselect certain Dock items if you don't want them to show previews. In addition to the main features of this app, there are also some additional touches, such as the ability to create and manage keyboard shortcuts for the app's controls, and the option to have windows snap automatically when you drag them to the edges of the screen.
HyperDock for Mac is a powerful and convenient program, with a lot of great features. It runs smoothly, and it's free to try for 15 days to see if it's something you'd like to use on a regular basis. If you do want to keep the program, you'll have to pay $9.95 for a full license, which seems a little high, even though the app does work quite well.