---
id: 5d822fd413a79914d39e98d2
title: Step 10
challengeType: 0
dashedName: step-10
---
# --description--
Nest a `div` with a class of `bb1` in the background buildings container. Open your `styles.css` file, and give `.bb1` a `width` of `10%` and `height` of `70%`. "bb" stands for "background building", this will be your first building.
# --hints--
You should create a new `div` element.
```js
assert.equal(document.querySelectorAll('div').length, 2);
```
You should give the new `div` a class of `bb1`.
```js
assert.exists(document.querySelector('div.bb1'));
```
You should use a `.bb1` class selector to style the element.
```js
assert.exists(new __helpers.CSSHelp(document).getStyle('.bb1'));
```
You should give the `.bb1` element a `width` of `10%`.
```js
assert.equal(new __helpers.CSSHelp(document).getStyle('.bb1')?.width, '10%');
```
You should give the `.bb1` element a `height` of `70%`.
```js
assert.equal(new __helpers.CSSHelp(document).getStyle('.bb1')?.height, '70%');
```
# --seed--
## --seed-contents--
```html
City Skyline
--fcc-editable-region--
--fcc-editable-region--
```
```css
* {
border: 1px solid black;
box-sizing: border-box;
}
body {
height: 100vh;
margin: 0;
overflow: hidden;
}
.background-buildings {
width: 100%;
height: 100%;
}
```