# Zettelkasten Zettelkasten is an analog [[Personal Knowledge Management|PKM]] system made popular by the sociology researcher Niklas Luhmann who famously had a Zettelkasten that consisted of 90,000 index cards, which he used to write dozens of books and hundreds of research articles. One of the basic ideas behind Zettelkasten is the split between literature and permanent notes. Literature notes extracts (citations) from sources, while permanent notes are your own thoughts, ideas, and insights that you develop while consuming content. ![[Zettelkasten Method - DeveloPassion#^8yf75p]] Regardless of type, all **notes should be future-proof and atomic[^1]**. ![[Zettelkasten Method - DeveloPassion#^tp95sy]] [^1]: ![[Atomic Notes - DeveloPassion#^516l05]]