3-year boys busy in construction skills training; see <a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=an5BYK9Etac">Video</a>. Courtesy of Alyona and Sergey
<a href="//commons.wikimedia.org/wiki/User:Shustov" title="User:Shustov">Shustov</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>