This source provides a comprehensive guide for citizen scientists interested in constructing CRISPR-based biosensors. It explains the fundamental principles of CRISPR technology, including the differences and applications of various Cas enzymes like Cas9, Cas12a, and Cas13a for detecting DNA and RNA. The text then outlines the complete workflow for a biosensor test, covering sample preparation, target amplification via isothermal methods (like RPA and LAMP), and diverse readout methodologies such as fluorescence, colorimetric assays, and lateral flow tests. Finally, it addresses the practical aspects of setting up a home laboratory, from sourcing reagents and equipment to navigating crucial safety protocols (BSL-1), legal considerations, and the ethical implications of DIY diagnostics.