# Testing Shadow DOM
> Shadow DOM is a new DOM feature that helps you build components. You can think of shadow DOM as a scoped subtree inside your element.\
> [polymer-project.org](https://polymer-library.polymer-project.org/2.0/docs/devguide/shadow-dom)
Shadow DOM is a technology that unlocks such features as isolated DOM and scoped CSS. It's usually used with custom elements to isolate their DOM from the global one. Puppetry targets are relative to a DOM scope (global or local). In order to query elements inside custom elements we have go with chained targets. So we are to create a target for the host element (the custom element root) and targets for the hosted sub-elements that point to the host target.
It's much easier to explain with an example. Imagine we have a custom element foo-component, built out of a template:
```markup
```
We can register the component with following code:
```javascript
document.addEventListener( "DOMContentLoaded", () => {
function registerCustomElement( elName, templateId ) {
globalThis.customElements.define( elName, class extends HTMLElement {
constructor() {
super();
this.attachShadow({ mode: "open" });
this.shadowRoot.appendChild( document.getElementById( templateId ).content );
}
});
}
registerCustomElement( "foo-component", "fooTemplate" );
});
```
Now if we inspect the page DOM with DevTools we can find the following sub-tree:
Let's say our goal is to access a local target (#shadowLocalTarget), hosted by foo-component element (fooShadowRoot).
> With DevTools you can inspect the target element and get with Copy/JS Path code like the that:\
> document.querySelector("#fooShadowRoot").shadowRoot.querySelector("#shadowLocalTarget")\
> If we translate it to Puppetry it actually gives us two targets:\
> \- shadow root: #fooShadowRoot \
> \- hosted element: #shadowLocalTarget, with the first target for the parent
What we have to do first is to create in Puppetry a target for foo-component (shadow root):
Then we create a target for the hosted element
The first one is a simple target like we are used to have in Puppetry, but the second is chained one. While building it we expand Options, set **Parent target** to `SHADOW_FOO` and **Parent type** to `shadow host`.
As soon as the hosted element target defined (`SHADOWDOM_FOO_LOCAL`) we can address it as any simple target:
