Hairy Bittercress,  Cardamine hirsuta
Brassicaceae or Mustard Family

Small plants with tiny white, four-petaled flowers.  Leaves of two kinds: basal leaves in a rosette with many, more-or-less egg-shaped leaflets, and stem leaves with long, narrow leaflets.  Fruits are long, straight pods which, at maturity, explode when touched, flinging seeds widely.  Blooms in early spring.

An alien, invasive weed, unfortunately very common along the Riverway and Wildwood Drive.  Also very common in yards and gardens.

Easily confused with other white-flowered mustards at first glance, but the leaves and long fruits are probably distinctive.