It's an annual activity created by Susanna Anderson in British Columbia. Rock-Flipping Day encourages naturalists and enthusiasts young and old to take a stroll through nature and to flip over a rock or two or three in order to peek at the tiny worlds that exist underneath. Walking through a park or along a beach, you're unlikely to give much thought to the little organisms and creatures living out their lives in homes tucked away from view. When you do flip a rock that gives up an unexpected surprise, you should then document your experience by taking a picture, writing a description, or even composing a drawing, anything that you can then share online with others. You can follow submissions on Susanna's blog, on the IRFD Flickr Pool, or on Twitter using the #rockflip hashtag. I myself took a moment to flip some rocks and this is what I found:

At a small rockbed located within the Toronto Music Garden, I flipped three small rocks. The first held a dead earwig and a pillbug, not too thrilling. The second, a trio of milky-white slugs.