I didn't know what they were yesterday morning as I surveyed the garden. But in the early morning light, just as the sun was rising, I saw a few minuscule mushrooms sprouted from the top of a damp bale of straw.
I find, after a little research, that they are part of the "Inky Cap" family, tiny mushrooms - Coprinoid Mushrooms - which are feasting on the straw itself. These "saprobes" assist in the decomposition of "wood, dung, grassy debris and forest litter". In other words, the tiny mushrooms were having breakfast on the rotting straw.
As the caps split, they take on the look of tiny "fungi flowers". These, in fact, are most likely a variety called "Non-inky Coprinus". I measured them at about 1/4" and that is their common size (though they may expand to as much as 5/8").
I noted their gray color and even a hint of lavender (the sunshine washes this out in the pictures). I am most surprised to find that they are edible (I'll skip that, though). They're common from May to October and a favorite habitat is noted as "lawns and grassy areas". They are particularly widespread in the eastern United States..
They're also known commonly as "Little Helmets".
Every tiny form of life finds its niche and makes haste to grow while the conditions are right. Our recent rains (not to mention my hose) have left the bales of straw damp and rotting and the warm, foggy night was the final impetus to growth. They appear in masses; what's perfect for one individual is perfect for them all.