They're practically the first weeds to bloom -- pretty sure it's bitter cress.
My kids love to pick them and when they go to seed, the little pods pop and scatter seeds everywhere so that the tiny seeds make pattering noises on their shoes, boots, and pant legs. They love to run through and scatter the seeds....
...so it's a good idea to hoe them down before they do go to seed.
...but if you uproot them, you'll find tons of earthworms congregating and ...well...
doing other things in the roots....