Question about ipod touch.

I have a new ipodtouch and a question about charging. I notice that if my ipod is on or in sleep mode it seems to charge with no problem. I can see the charging display on my PC in itunes.(like the little battery icon thing). But if my ipod is completely off it doesn't show anything and doesn't appear to charge...is it actually charging if it's off or do I need to leave it on or in sleep? Thank you...

Normally when it is charging it will a battery logo will appear on screen saying it is charging.