Images and ideas about real and abstract things, and how they are related--including the meaning of ""related."" Kriss and Kross have invented a wonderful transformation machine: put three things in the left-hand side, and four come out on the right; change the controls, and put a frog in the left, and out comes a tadpole on the right. Mostly the machine works both ways, but with one setting--one that reduces complex colored objects to their all-gray shapes--it works only one way, because there is no relationship between a gray shape and an arbitrarily complex set of colors. So when are things the same, and when different? How can you describe them? How can you measure them? Anno is a subtle and careful thinker who has been thinking for a long time about showing young readers the power and complexity in simple ideas. Sly humor abounds on every page here; when the artist illustrates how a picture can be drawn with dots, Kriss points out to Kross that he too is composed of dots. While even small children are capable of understanding these essential ideas, the book will need to be introduced to them--but only to the point where the child grasps the logic.