Lab-on-a-Chip (LoC)Lab-on-a-Chip (LoC) technology leverages microfluidics to enable miniaturized, efficient, and portable diagnostic assays. This chapter explores the fundamental properties of microfluidic flows, including the controlled movement of liquids and particles within chip-based systems. Key materials and manufacturing technologies, such as substrate selection, microfabrication techniques, and bonding methods, are discussed to highlight their role in LoC development. Additionally, reagent pre-storage strategies—both in liquid and dry forms—are examined to ensure assay stability and reliability. The integration of biosensors for analyte detection is essential for accurate diagnostics, while micro-macro interfaces and sample preparation techniques play a crucial role in bridging laboratory and real-world applications. Finally, the chapter outlines diverse application areas, from point-of-care medical diagnostics to environmental monitoring and food safety, demonstrating the transformative impact of LoC systems in on-site analysis.