Great Caesar's Ghost!! If you are growing this plant for herbal use (not exactly decorative flowers or berries for the garden outside or home indoors) I hope you know what you are doing growing it indoors. Hysteria aside:) the roots of these plants like to spread out and down a bit so the plant will stay small and probably will never bloom in the pots they are in. Planting them outside will give the roots a chance to spread so the plant can get bigger and mature to a flowering and subsequent berry producing stage.

I have just brought them in for the winter I am going to put them back in the ground for the spring. I have a third in a much bigger pot and they seem to keep growing well even in the other smaller pots from the picture, but we'll see I love this plant!

Atropa belladonna is totally hardy, I would put them in the ground now if it's not actually freezing. It is a terrible thug and will spread everywhere. I've been trying to eradicate it from my garden for years (grandchildren!).

Are you aware that every part of this plant is very poisonous, and ingesting just two berries will kill a child?
Granted a lot of garden plants are poisonous, but having this in the house????

Landgirl and Stera are right about this plant, it would rather kill than be killed; it is very hardy and very poisonous. Whatcha got going in that little seed starter tray in front of the Deadly Nightshade Foreignpolicy? Welcome to GOY!

Yes, welcome, Foreignpolicy! What general part of the country are you gardening in? We don't need to know your address, but we can give more intelligent advice if we know about what climate you're dealing with.
In light of that, Landgirl, it might be more marginal where Foreignpolicy lives, at least enough to worry about new seedlings. My research shows that it is only hardy down to about -24º C (-10º F), and many parts of the U.S. get much colder.