Identify this for me please

[bigfatskinny]

Can someone please tell me what the pinkish red thing with dots is? I found it under Maples, Oaks, and Beech trees. P.S. The acorns are just starting to drop in lower Michigan.

 

[Native Hunter]

Yep, those are acorn plum galls.

 

[Bszweda]

I always wondered what the heck those things were