Nightmares

Didn't know that our little babies could have nightmares! My poor guy woke up from a dead sleep just screaming his little head off completely freaked out and when I Ran upstairs to see what was wrong and comfort him he just was holding onto me around my neck for dear life whimpering and just so sad it was awful the poor thing!! So with no physical things being wrong I assume the poor thing had a nightmare. How terrible would that be?! Barely understanding the world to have to wake up so confused and scared.