Our mushroom kit has been busily growing. It said it would take 7-10 days to get started, so I didn't worry at first. But even at 10 days, there wasn't really anything there. Slowly, we got these little teeny, tiny spots. I figured they must be baby mushrooms, but they weren't much to look at. The packaging said they would double in size daily. Well... not at first. But then they got to a decent sort of size, as below:
At first I thought the clump of mushrooms was the button type, but then they got bigger and browner and the lone mushroom popped up in the corner. That one really did seem to pop up out of nowhere, so it must have at least doubled overnight! We're still not exactly sure when they are "full grown" and ready to be picked, but probably by this weekend.