Structural directives change the layout of the HTML document by adding and removing elements. They build on the core features available for attribute directives, described in Chapter 15, with additional support for micro-templates, which are small fragments of contents defined within the templates used by components. You can recognize when a structural directive is being used because its name will be prefixed with an asterisk, such as *ngIf or *ngFor. In this chapter, I explain how structural directives are defined and applied, how they work, and how they respond to changes in the data model. Table 16-1 puts structural directives in context.