Connect with your students' prior knowledge! Students' conceptions are a classic topic in psychological and subject-specific educational research. Without a detailed understanding of these conceptions, it is hardly possible to build on students' prior knowledge and teach biology effectively. Nevertheless, research findings on students' conceptions are rarely utilized in classroom practice, even though this would be sensible from the perspective of constructivist learning theories, as prior knowledge significantly determines what is learned. The authors describe essential student conceptions from various areas of biology (metabolism, ecology, evolution, genetics, human biology, cytology) and support these with examples from research. Additionally, they compare these with scientific concepts and discuss their relevance for biology education.