This chapter presents the fundamental principles governing the storage and handling of cohesive bulk solids, with a focus on the design of gravity-fed storage bins and hoppers. It outlines a systematic design philosophy that integrates bulk solid flow properties, bin geometry, stress fields, and discharge requirements to achieve reliable and predictable performance. The principal modes of flow, mass-flow and funnel-flow, are defined and compared, highlighting their operational advantages, limitations, and suitability for different materials. The chapter emphasises the pivotal contributions of Jenike’s theory, including stress field concepts, yield loci, flow functions, wall friction, and flow factors, which together form the basis for modern bin design. Detailed discussion is provided on the selection of hopper geometry, hopper half-angles, and critical opening dimensions required to prevent arching and ratholing. Variations such as expanded-flow bins are also introduced for large-capacity applications. Overall, the chapter establishes the theoretical framework and key design considerations necessary for safe, efficient, and dependable bulk solids storage systems.