We will encounter the copy maps again in Section 8.2.2 when expressing classical datain diagrammatic terms. Decorations such as the π in the case of the NOT gate will beexplained in Section 9.1, and the interaction of the two colours will be explained in Section9.2. All of these pieces together will play an important role in a very powerful diagrammaticlanguage called the ZX-calculus, described in Section 9.4.