Mimosa.

These are the leaves of a Mimosa (sometimes called Silk) tree (Albizia julibrisson), which can be very invasive in the South but not so much here as we're on the edge of its coldest zone. Southeastern Pennsylvania is Zone 6b, so certain plants like the Mimosa and Crape Myrtle can die back to the ground over a harsh winter but recover the next year. Most interesting factoid: Mimosa leaves fold up at night, I guess to sleep better.

To take these photos the sun has to have just risen into the Mimosa leaves, with the shrub border in the background still in shadow.