How long does it take to get from antioxidants to glycogenolysis during rush hour? This Wiki-linked diagram of a metabolic network resembles a subway map, and it displays the striking complexity of human biochemistry.
It's fun to mouse over the pretty colors whether you're a practicing biochemist or a curious beginner— though nonexperts may find themselves on the "peak of Mount Stupid" on the Dunning Kruger curve.
The metro-style map was created by User:Chakazul, whose user page contains a gallery of other scientific diagrams that I've enjoyed clicking through. I'm continually inspired by the beautiful things that people make for strangers.