[Plugin: NextGEN Gallery] <?php wp_head(); ?> missing?

Just thought I’d post my findings since I wasn’t able to directly find the answer here. I was able to fix my problem but only after some trial and error.

NextGEN Gallery was the first plugin I have used that required the wp_head() tag in my customer theme so I had to figure out how to add this and how it worked.

Issue: Gallery displayed but no styling was applied and the thickbox effect did not work.

Resolution: I was able to identify that no html was being generated in the head tag like it was when I switched my site over to the default theme. This told me I was missing something that generated that html code, wp_head() was that answer. I was able to get it to work by placing <?php wp_head(); ?> in my header.php just above the closing </head>.