I noticed that the birds were behaving a little differently around the nest this afternoon, instead of sitting on the eggs, they were both flying to and fro, sitting on the edge of the nest and reaching down into it. When they were off on a worm-run, I took a photo:
Later, we took another peak:
They are pretty small and ugly right now, and only make little cheeping sounds. But already Mother and Father Robin are working pretty hard!