When do I take transplanted plants from under lights

I'm gonna learn all this, I promise. This is the first year I've grown plants under lights, so I know nothing.
Seeds have germinated, got big enough to transplant to a larger pot, like 3 inches. How long do I leave them under lights or do I grandually take them out.
I have a lot that's come up and has enough leaves to transplant, but just don't want to kill them!!!

I'd leave them under lights until you move them outside. Once they're planted outside, then the sun will take care of them, but until then if you don't keep them under lights they'll start to get leggy on you. (when you get ready to take them outside, you do need to adjust them gradually to outdoor temperatures and amount of sun...your indoor lights have nothing on the sun in terms of intensity, so if you just dump them outside in full sun their leaves will get sunburned)

We have had nice 70 degree daytime temps and I took all my flats out from under the lights last Friday and giving them increasing amounts of sunshine daily. My plan is to transplant them into the gardens on Sunday. Today they received 5 hours of direct sunshine and they are loving it. Last friday I gave them 1 hour and some drooped a bit. Since then they have grown an inch or two. Should be ready!

Lorraine, here's a tip that I remember reading last year in another thread that I said I was going to try this year: When you are ready to bring your transplants out, put them under a plastic laundry basket. The large holes in the sides will allow a lot of light to filter through, but will still provide them with some protection. I was surprised to find last year that my plants actually had sunburn because the sunlight was so strong compared with the plant lights.

That's a good idea!! We've been having a really warm spell here, so it feels like spring and I was tempted to take some of the bigger ones out for a while, but then found out it will be 35 tonight and 50 tomorrow, which is cold for us. I'm sure we'll have one more freeze before spring because we always do. My dad was a farmer when he was younger and he always said "Don't plant until Good Friday." Of course, I thought I knew better so I'd plant things and put stuff out before and always lost them. You'd think I would have learned after the first time, but noooooo.