Vine found in crack in concrete

[ApidAdi]

So I pulled this plant out of a crack in the sidewalk, and at the time I thought it was a Nightshade. Now, however, I'm not so sure - it's grown from a shrubby little dark green/purpley plant into a full on verdant vine. I know there's a viney Nightshade called bittersweet, but the leaves really don't look like this. It may be that it's quite young, and the leaves will change with time, who knows. But I am thoroughly baffled.

 

[Marck]

This is Climbing Hemp-vine (Mikania scandens) in the Boneset tribe (Eupatorieae) of the Daisy Family (Asteraceae).
It is native to the eastern United States and northeastern Mexico.