Media-Query-Mixin for Sass | Code found here: http://thesassway.com/intermediate/responsive-web-design-in-sass-using-media-queries-in-sass-32

SassMeister-input.scss

// ----
// Sass (v3.2.14)
// Compass (v0.12.2)
// ----

$break-small: 320px;
$break-large: 1024px;

@mixin respond-to($media) {
  @if $media == handhelds {
    @media only screen and (max-width: $break-small) { @content; }
  }
  @else if $media == medium-screens {
    @media only screen and (min-width: $break-small + 1) and (max-width: $break-large - 1) { @content; }
  }
  @else if $media == wide-screens {
    @media only screen and (min-width: $break-large) { @content; }
  }
}

.profile-pic {
  float: left;
  width: 250px;
  @include respond-to(handhelds) { width: 100% ;}
  @include respond-to(medium-screens) { width: 125px; }
  @include respond-to(wide-screens) { float: none; }
}

@include respond-to(handhelds) { 
  .test {color: red;}
}
@include respond-to(medium-screens) { 
  .test {color: blue;}
}

SassMeister-output.css

.profile-pic {
  float: left;
  width: 250px;
}
@media only screen and (max-width: 320px) {
  .profile-pic {
    width: 100%;
  }
}
@media only screen and (min-width: 321px) and (max-width: 1023px) {
  .profile-pic {
    width: 125px;
  }
}
@media only screen and (min-width: 1024px) {
  .profile-pic {
    float: none;
  }
}

@media only screen and (max-width: 320px) {
  .test {
    color: red;
  }
}
@media only screen and (min-width: 321px) and (max-width: 1023px) {
  .test {
    color: blue;
  }
}