Want to know what is going on in OS X when you boot? Trying to find out why your system will not boot? By booting with verbose mode, you can see everything going on behind the scenes during the boot-up process.

In trying to install the latest version of OS X, I would just get the reboot screen after about 5 minutes. I couldn't figure out what was going on.

By booting up into verbose mode, I could see where in the boot-up process I was getting the panic.

Reboot the system and as it starts to come up hold down the following keys:

CMD-V

Instead of the typical pretty start-up screen, you'll see the boot-up process with white on black text.