Each icon opens a group of units. Finish a topic's short quiz to unlock the next one — your path is shown any time in the Pathway sidebar.
This is how a microbiologist actually narrows down an unknown bacterium — one identifying feature at a time. Tap any box to branch further; tap a highlighted organism to see its key facts.
Jump back into any topic to try again.
Every box below is a unit. Locked topics need the topic before them finished first.