diff --git a/book/book.tex b/book/book.tex
index fa711b3..9daaa29 100644
--- a/book/book.tex
+++ b/book/book.tex
@@ -56,9 +56,11 @@ produce a lot of \ch{CO2}.
 \end{center}
 \end{figure}
 
+% In this case generate the graphic with pdflatex first: pdflatex fig-life-planet-sourdough-timeline-external.pdf
+% Then it will show up properly.
 \begin{figure}[!htb]
   \includegraphics{figures/fig-life-planet-sourdough-timeline-external.pdf}
-  \caption{Embedding pre generated pdf works}
+  \caption[Sourdough microbiology timeline]{Timeline works embedded as pdf}%
 \end{figure}
 
 \begin{figure}[!htb]