If you have AT&T for iphone 5s do they pre-install the SIM card into your device?

I'm curious because I'm gonna be purchasing an iphone 5s, 2 year contract plan they have. An so I've been lookin at the reviews an I noticed there's a SIM card needed. I read somewhere it was pre installed but I'm curious if there's anyone who has a plan with AT&T an could tell me if it is pre-installed or not.

They put the sim card into the phone when they activate it.