Heavy rain.
This must be my most common Mycena: it's everywhere at the moment.
I'm pretty sure that this one is Mycena epipterygia - it has a yellow area at the top of the stipe.
This is more likely to be a Hemimycena. The cap is about 3mm across.
A droplet of water acts as a magnifying glass on the blade of grass.
Lastly, the seeds of Square-stalked St. Johns Wort.