component2.html

<link rel="import" href="https://www.polymer-project.org/1.0/components/polymer/polymer.html">
<link rel="import" href="https://gist.githubusercontent.com/ckimrie/22718bfead15b8903b9f7a616342d19f/raw/cedbff08823c585c7d2eebd8ef94d1b204438a50/component.html">

<dom-module id="component-2">
  <template>
    <style include="component-1">
      :host {
        display: block;
      }
    </style>
    <div id="target"></div>
  </template>
  <script>
  (function() {
    'use strict';

    Polymer({
      is: 'component-2',

      properties: {
        foo: {
          type: String,
          value: 'component-2',
          notify: true
        }
      },
      ready: function(){
        var el = document.createElement('div');
        el.className = 'red-box';
        el.textContent = 'Hello';
        this.$.target.appendChild(el);
      }
    });
  })();
  </script>
</dom-module>