I have a medium sized container where i have planted three or four different kind of seeds...but i don't think this is one of them. I'm pretty sure it came up and grew nicely of its own accord.

There are some "weeds" that i consider desirable but i don't think this is going to be one of them.

An ID would really be appreciated. The flowers you see fully opened are 2cm (.79 of an inch) wide) and have delicate petals. Any ideas?

Possible tomatillo, or other nightshade.

Looks like something from the Nightshade Family, Solanaceae.

Unusual flowers.

Thank you Stone and Metro...i will root around in the Solanaceae images and see if i can find a match. I have two new Solanaceae in the garden this year (from seed, Cestrum nocturnum) that will grow quite large, so i will probably not keep this newcomer. The Cestrum is a host plant for some Clearwing butterflies that i have not seen in the garden yet so i am looking forward to that and also to stinking up the entire neighborhood with the Night-blooming Jasmine

Yep, Solanum of some type. It reminds me a lot of Black Nightshade (Solanum americanum) that we have here in Florida but they all look a lot alike to me.