Biology can look like a pile of names to memorise. It is not. Underneath, a small number of mechanisms do most of the work, and once you see them the details fall into place. These pages aim for the mechanism, not the vocabulary: how the thing actually works, and how we know.
The deepest thread is information. Every cell carries its instructions as DNA, and the rules for reading them, the central dogma, are the foundation everything else sits on. From there follow the tools and failure modes of that system: CRISPR gene editing, the protein folding problem and what AlphaFold solved, prions (proteins that misfold and spread), and cloning.
A second thread is evolution, the process that shaped all of it. Natural selection is the engine; antibiotic resistance is that engine caught in the act, on a timescale of days, and one of the most urgent problems in medicine. Run the tape all the way back and you reach the hardest question of all, the origin of life: how chemistry first crossed the line into biology.
A third thread is living systems at work: how the immune system learns to recognise a threat, how neurons fire and carry a signal, how photosynthesis turns sunlight into food, and how an infection spreads through a population (epidemics and the SIR model), where biology meets mathematics.
Every explainer below is written at three depths on the same page. Level 1 is for a curious twelve-year-old, Level 2 for someone who has just finished school, and Level 3 for an undergraduate. Pick a depth, and change it whenever you want more detail or less.