Scientific experiments play a crucial role in acquiring reliable knowledge about the natural world and its phenomena. Still, they must be appropriately designed so that the resulting data are precise and accurate. This chapter focuses on the main components of an experiment (e.g., the hypothesis, treatments, their allocation to experimental units, and variables). It presents the three fundamental techniques to obtain valid data: control, true replication, and randomization. Reasons to support the adoption of these three techniques are discussed, and several examples of valid and invalid experiments are provided, enabling readers to build a solid foundation for scientifically sound research in agriculture.