(Rubiaceae) - This diminuative woodland flower belongs to the bedstraw family.
Bluets also go by several quaint names; "Quaker Ladies", "Innocence", and "Little-Washerwoman".
The general identification rule is that these flowers have 4 petals, although in this photo some seem to have 5...
Bluets bloom in late spring to early summer.
(Photographed in PA)