The development of electrochemical and biosensors hinges on the strategic selection of materials in a layered "stack-up" configuration. Each material plays a distinct role in optimizing sensor sensitivity, stability, and performance. Advances in materials, substrates, and functionalized compounds have driven the evolution of these sensors, enabling their application across a wide range of fields, from healthcare to environmental monitoring. This talk explores the importance of material design in enhancing sensor functionality, highlighting key materials and emerging trends, while addressing the challenges of integrating these layers for high-performance systems.