What Part of iPhone is this?

[WhiteIphone5]

my iPhone became really hot, i opened it and the battery seem warm but on the left side its really hot, like really hot!
i circled the part where it started becoming extremely hot.

 

[dictoresno]

the phones main processor, the A4 chip for your iphone 4, is directly under where you circled.

 

[MrMacMack]

Yep you found yourself a cooking hot processor that's processing.