For quite some time now, computing systems servers, whether low-power or high-end ones designs are created around a common design principle: the main-board and its hardware components form a baseline, monolithic building block that the rest of the hardware/software stack design builds upon. This proportionality of compute/memory/network/storage resources is fixed during design time and remains static throughout machine lifetime, with known ramifications in terms of low system resource utilization, costly upgrade cycles and degraded energy proportionality. dReDBox takes on the challenge of revolutionizing the low-power computing market by breaking server boundaries through materialization of the concept of disaggregation. Besides proposing a highly modular software-defined architecture for the next generation datacentre, dRedBox will specify, design and prototype a novel hardware architecture where SoC-based microservers, memory modules and accelerators, will be placed in separated modular server trays interconnected via a high-speed, low-latency opto-electronic system fabric, and be allocated in arbitrary sets, as driven by fit-for-purpose resource/power management software. These blocks will employ state-of-the-art low-power components and be amenable to deployment in various integration form factors and target scenarios. dRedBox aims to deliver a full-fledged, vertically integrated datacentre-in-a-box prototype to showcase the superiority of disaggregation in terms of scalability, efficiency, reliability, performance and energy reduction which will be demonstrated in three pilot use-cases.