and the answer is...

1 (one one)
11 (two ones)
21 (one two, one one)
1211 (one one, one two, two ones)
111221 (three ones, two twos, one one)
312211 (one three, one one, two twos, two ones)
13112221 and so on.

Sorry - it amused me for a little while!

A Puzzle

Now that I know the answer, I think this is really clever. See what you think. (apologies for stealing it from elsewhere).
What's next in the sequence?
1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, .......