function processItem(el, settings){
    if (!isElement(el) || (!settings.reProcess && el.getAttribute('textFitted'))) {
      return false;
    }

    // Set textFitted attribute so we know this was processed.
    if(!settings.reProcess){
      el.setAttribute('textFitted', 1);
    }

    var innerSpan, originalHeight, originalHTML, originalWidth;
    var low, mid, high;

    // Get element data.
    originalHTML = el.innerHTML;
    originalWidth = innerWidth(el);
    originalHeight = innerHeight(el);

    // Don't process if we can't find box dimensions
    if (!originalWidth || (!settings.widthOnly && !originalHeight)) {
      if(!settings.widthOnly)
        throw new Error('Set a static height and width on the target element ' + el.outerHTML +
          ' before using textFit!');
      else
        throw new Error('Set a static width on the target element ' + el.outerHTML +
          ' before using textFit!');
    }

    // Add textFitted span inside this container.
    if (originalHTML.indexOf('textFitted') === -1) {
      innerSpan = document.createElement('span');
      innerSpan.className = 'textFitted';
      // Inline block ensure it takes on the size of its contents, even if they are enclosed
      // in other tags like <p>
      innerSpan.style['display'] = 'inline-block';
      innerSpan.innerHTML = originalHTML;
      el.innerHTML = '';
      el.appendChild(innerSpan);
    } else {
      // Reprocessing.
      innerSpan = el.querySelector('span.textFitted');
      // Remove vertical align if we're reprocessing.
      if (hasClass(innerSpan, 'textFitAlignVert')){
        innerSpan.className = innerSpan.className.replace('textFitAlignVert', '');
        innerSpan.style['height'] = '';
        el.className.replace('textFitAlignVertFlex', '');
      }
    }

    // Prepare & set alignment
    if (settings.alignHoriz) {
      el.style['text-align'] = 'center';
      innerSpan.style['text-align'] = 'center';
    }

    // Check if this string is multiple lines
    // Not guaranteed to always work if you use wonky line-heights
    var multiLine = settings.multiLine;
    if (settings.detectMultiLine && !multiLine &&
        innerSpan.scrollHeight >= parseInt(window.getComputedStyle(innerSpan)['font-size'], 10) * 2){
      multiLine = true;
    }

    // If we're not treating this as a multiline string, don't let it wrap.
    if (!multiLine) {
      el.style['white-space'] = 'nowrap';
    }

    low = settings.minFontSize + 1;
    high = settings.maxFontSize + 1;

    // Binary search for best fit
    while (low <= high) {
      mid = parseInt((low + high) / 2, 10);
      innerSpan.style.fontSize = mid + 'px';
      if(innerSpan.scrollWidth <= originalWidth && (settings.widthOnly || innerSpan.scrollHeight <= originalHeight)){
        low = mid + 1;
      } else {
        high = mid - 1;
      }
    }
    // Sub 1 at the very end, this is closer to what we wanted.
    innerSpan.style.fontSize = (mid - 1) + 'px';

    // Our height is finalized. If we are aligning vertically, set that up.
    if (settings.alignVert) {
      addStyleSheet();
      var height = innerSpan.scrollHeight;
      if (window.getComputedStyle(el)['position'] === "static"){
        el.style['position'] = 'relative';
      }
      if (!hasClass(innerSpan, "textFitAlignVert")){
        innerSpan.className = innerSpan.className + " textFitAlignVert";
      }
      innerSpan.style['height'] = height + "px";
      if (settings.alignVertWithFlexbox && !hasClass(el, "textFitAlignVertFlex")) {
        el.className = el.className + " textFitAlignVertFlex";
      }
    }
  }
The meat. Given an el, make the text inside it fit its parent.
@param  {DOMElement} el       Child el.
@param  {Object} settings     Options for fit.