The story in three lines. Tí and Bà Tư make breakfast. Ice melts and freezes again; dough squashes and rolls back. Then the egg turns from clear to white, Tí says "again", and it will not go back.

One question to ask. "Can we make it go back?" Ask it about everything for a week: a melted ice lolly, a folded towel, a broken cracker, a puddle. Some answers are "yes", some are "no", and some are "a bit". All three are good answers.

One thing to do at the table. Make two bowls with a paper label each, BACK and STAY, or cut out the card from the book. At breakfast, put things in them, or just point: a cube of ice (back), a slice of toast (stay), a squashed ball of play dough (back), a cracked eggshell (stay).

The grown-up layer. An egg white is mostly water and protein. Heat shakes the protein chains loose from their folded shapes and they tangle together; that tangle is what turns the white from clear to solid, and it does not untangle when it cools. Melting ice is different: the water is the same stuff, only arranged differently, and cold arranges it back. You don't need any of this with a four-year-old. "Some things go back; some things stay" is the whole idea, and wanting it to go back is part of learning it. Years from now, the Fold Commons stories tell the surprising other half: some proteins do fold back.

Let your child say the last words of each line on the second morning. By the fifth morning, let them tell it to a toy.