iPhone Home Screen App icons turn grey for a second randomly (blinks) What's the meaning of it?

Hello guys, i've just got my first iPhone (7), and i'm kinda new to the iOS and everything, but today i've noticed something that i'm not exactly sure what it was, but it seemed like some of my App's icons on my homescreen blinked (turned grey) for just a sec, is there any information on what was happening?

My guess is from what i've read is that it might be some kind of auto-optimization, or cleaning process, can someone confirm this, or have any official information on this?