The .flatMap() case is a bit more complex:

The operator here says that each received item is replaced by two new items that will be diamond shaped. After the two items are emitted, the sequence terminates normally (the vertical dash sign).

As we can see in the preceding figure, in the resulting Observable, each of the items was replaced by two elements. However, it emphasizes that the order of the items can be changed, because there is a green item after a blue one.