A very tiny mushroom

I found this little mushroom the morning of Aug. 21. It was growing alone in a shady area near a pond. I found several kinds of mushrooms on this morning. But this one was the most interesting one to me.

My research revealed that it is commonly known as a Japanese umbrella mushroom. This kind of mushroom is found in Japan, Europe and North America.

The acorn was laying on the ground a short distance away, where I presume a squirrel dropped it. I placed it beside the Japanese umbrella for size reference. The acorn is 5/8 of an inch at its widest point.