<p>Allen dives in to diodes, Arik explores the origin of taxis, and Allen reveals an unsavoury fact about zygotes.</p>
<ul>
<li><a href="https://www.youtube.com/watch?v=6WGKz2sUa0w">Steve Mould on LEDs and solar panels</a></li>
<li><a href="https://www.youtube.com/watch?v=AF8d72mA41M">Why blue LEDs were almost impossible</a></li>
<li><a href="https://en.wikipedia.org/wiki/Thornton_Blackburn">Thornton Blackburn</a></li>
</ul>
