Why I Switched to Zettelkasten for Biomedical Science Notes (And How to Start)

The Problem With Linear Notes

For the first few weeks of university, I took notes the way I always had: linearly. Lecture by lecture, topic by topic, in neat sequential order in a notebook or a Word document.

The problem became apparent when I started revising. Biochemistry, cell biology, and physiology are not separate subjects — they're deeply interconnected. A concept in biochemistry explains a mechanism in cell biology that underpins a process in physiology. But my notes treated them as separate silos. When I tried to connect them, I had to flip between three different notebooks or scroll through three different documents.

I needed a system that reflected how the knowledge actually worked.

What Is Zettelkasten?

Zettelkasten is a note-taking method developed by German sociologist Niklas Luhmann, who used it to write over 70 books and 400 academic articles. The name means "slip box" in German — Luhmann's original system was a physical box of index cards.

The core principle is simple: each note contains one idea, and notes are connected to each other through links. Instead of a linear hierarchy (topic → subtopic → detail), you build a network of connected ideas.

How I Apply It to Biomedical Science

I use Obsidian, a free note-taking app that stores notes as plain text Markdown files and allows you to link between them. Each note I create covers one concept — not one lecture, not one topic, but one concept.

For example, I have a note on the G1/S checkpoint. That note links to notes on p53, CDK4/6-cyclin D, Rb protein, and DNA damage response. Each of those notes links to others. Over time, I've built a network where I can start at any concept and follow the connections to understand how it fits into the broader picture.

The Practical Workflow

During lectures, I take rough notes in a temporary "inbox" — just capturing information quickly without worrying about structure. After the lecture, I process these into permanent notes in Obsidian, one concept per note, with links to related concepts.

This processing step is itself a learning activity. Deciding what connects to what forces you to think about the relationships between concepts, which is exactly the kind of deep processing that produces long-term retention.

The Compound Effect

The real power of Zettelkasten becomes apparent over time. After a few months, I have hundreds of connected notes. When I encounter a new concept, I can immediately see how it connects to things I already know. New knowledge integrates into an existing structure rather than sitting in isolation.

This is how experts think. They don't have more information than novices — they have better-connected information. Zettelkasten is a tool for building that kind of connected knowledge deliberately.