Block Element Modifier is a methodology that helps you to create reusable components and code sharing in front-end development

Easy

To use BEM, you only need to employ BEM’s naming convention.

Modular

Independent blocks and CSS selectors make your code reusable and modular.

Flexible

Using BEM, methodologies and tools can be recomposed and configured the way you like.

// main.scss
.pony {
    @import 'sub';
    font-size: 100px;
}

// _sub.scss
.chow {
    color: tomato;
}

Will compile to:

.pony { font-size: 100px; }
.pony .chow { color: tomato; }