<===> input.scss
.md-card
{
    .md-info-card-highlight
    {
        background: red;
        color: blue;

        .ng-md-icon
        {
            color: green;
        }
    }
}
<===> output.css
.md-card .md-info-card-highlight {
  background: red;
  color: blue;
}
.md-card .md-info-card-highlight .ng-md-icon {
  color: green;
}