<===> input.scss
.foo {
  content: foo;

  @media only screen and (min-width: 1337px) {
    content: bar;

    @media only screen and (max-width: 42em) {
      content: baz;
    }
  }
}

<===> output.css
.foo {
  content: foo;
}
@media only screen and (min-width: 1337px) {
  .foo {
    content: bar;
  }
}
@media only screen and (min-width: 1337px) and (max-width: 42em) {
  .foo {
    content: baz;
  }
}