Adding chicks to the flock

What's the best age to introduce chicks into the flock? I have nearly 7 week old chicks. They are in the coop already, but separated on one side. They can see the "grown-up girls" through the wire door, but have yet to meet the roos since they are camping out in the run right now.

I'm interested in the response to this topic as well.......

We haven't incorporated their ranging til 8-12 weeks. We would usually have them in a tractor with large chicken wire run where the young are put in around 6 weeks old. After another 4-6 weeks when they are starting to get 2/3-3/4 or so of the size of the adults then we open the door to the run. The adventurous ones go out, the rest stay in til they are ready to explore. Not many hens go in the run, just the odd nosy one. Over the course of a week or two the young will all go out and mix, silkies often take longer. The young then have a relatively safe spot and we watch for bully adults going in to the babies tractor. Usually they are just doing a hit and run on the food if theirs is low That's our routine and it seems to work OK! They are not housed together at night usually til September-October time when the young from Mar-June hatches need a winter-non-tractor home.