The SOLID concept is to develop small solid-state hybrid systems capable of performing elementary processing and communication of quantum information. This involves design, fabrication and investigation of combinations of qubits, oscillators, cavities, and transmission lines, creating hybrid devices interfacing different types of qubits for quantum data storage, qubit interconversion, and communication. The SOLID main idea is to implement small solid-state pure and hybrid QIP systems on common platforms based on fixed or tunable microwave cavities and optical nanophotonic cavities. Various types of solid-state qubits will be connected to these "hubs": Josephson junction circuits, quantum dots and NV centres in diamond. The approach can immediately be extended to connecting different types of solid-state qubits in hybrid devices, opening up new avenues for processing, storage and communication. The SOLID objectives are to design, fabricate, characterise, combine, and operate solid-state quantum-coherent registers with 3-8 qubits. Major SOLID challenges involve: Scalability of quantum registers; Implementation and scalability of hybrid devices; Design and implementation of quantum interfaces; Control of quantum states; High-fidelity readout of quantum information; Implementation of algorithms and protocols. The SOLID software goal is to achieve maximal use of the available hardware for universal gate operation, control of multi-qubit entanglement, benchmark algorithms and protocols, implementation of teleportation and elementary error correction, and testing of elementary control via quantum feedback. An important SOLID goal is also to create opportunities for application-oriented research through the increased reliability, scalability and interconnection of components. The SOLID applied objectives are to develop the solid-state core-technologies: Microwave engineering; Photonics; Materials science; Control of the dynamics of small, entangled quantum systems