Those tiny seedlings will develop true leaves and show growth as soon as you get good stretches of warmer weather. You will be amazed at how fast they can grow. In the meantime, they are developing roots.

You can plant out babies after they have those true leaves. Begin with hardy perennials and hardy annuals like poppies and BBs. You might wait to plant out those tender annuals (like zinnias) until you are fairly sure you are past your last frost.

Karen

Just_me: Last year was my first year, and I put my containers in several spots, some being in full sun, just to see what worked best. The containers didn't care where they were, they all grew equally. The only difference I found was that the ones in full sun dried out a lot quicker, and if I didn't either take the top off during the day if it got too warm they fried. I too would wait until they get their first true leaves. They will be a little stronger come plant out time. Good luck!