session-desktop/stylesheets/_emoji.scss

span.emoji {
  display: -moz-inline-box;
  -moz-box-orient: vertical;
  display: inline-block;
  vertical-align: baseline;
  width: 1em;
  height: 1em;
  background-size: 1em;
  background-repeat: no-repeat;
  text-indent: -9999px;
  background-position: 50%, 50%;
  background-size: contain;
}

span.emoji-sizer {
  line-height: 0.81em;
  font-size: 1em;
  margin: -2px 0;
}

span.emoji-outer {
  display: -moz-inline-box;
  display: inline-block;
  height: 1em;
  width: 1em;
}

span.emoji-inner {
  display: -moz-inline-box;
  display: inline-block;
  text-indent: -9999px;
  width: 100%;
  height: 100%;
  vertical-align: baseline;
}

img.emoji {
  width: 1em;
  height: 1em;
  margin-bottom: -1px;
}

img.emoji.small {
  width: 1.1em;
  height: 1.1em;
}
img.emoji.medium {
  width: 1.3em;
  height: 1.3em;
}
img.emoji.large {
  width: 1.7em;
  height: 1.7em;
}
img.emoji.jumbo {
  width: 2em;
  height: 2em;
}

// we need these, or we'll make conversation items too big in the left-nav
.conversations img.emoji.small {
  width: 1em;
  height: 1em;
}
.conversations img.emoji.medium {
  width: 1em;
  height: 1em;
}
.conversations img.emoji.large {
  width: 1em;
  height: 1em;
}
.conversations img.emoji.jumbo {
  width: 1em;
  height: 1em;
}