The phrase "mouse droppings" refers to the small, dark, and cylindrical waste that mice leave behind. It is often used to describe tiny, insignificant, or unimportant things. Full definition
Ten cats, likely lazy because the kitchen counter is covered in mouse droppings. (remonline.com)
On the way into the lab I notice mouse droppings on the floor and some discarded, damaged equipment on shelves with tags labeled «NFG» attached. (discovermagazine.com)
Found these on Amazon and (as one of the only chia seed packages that didn't have reviews citing found mouse droppings) decided to give it a go. (amazon.com)