The Universal Access area of your System Preferences is one of the least used places on most Macs…but it is filled with cool and interesting things you can do on your Mac. One such thing is zooming. You can zoom in and out of your screen just like if you were using an application like Photoshop, but you can zoom anywhere, for anything.
To enable this simply press Command-Option-8 (you can press this again to disable it). After you have turned it on, you can press Command-Option-Equals(+) to zoom in and Command Option-Dash(-) to zoom out.