This master's thesis explores innovative solutions for satellite subsystems miniaturisation, with a specific focus on technologies that could enable the design and development of femtoSatellites, which are small satellites weighing less than 100 grams. After a concise review of the main spacecraft subsystems, the possibility to miniaturise existing devices will be investigated and innovative solutions will be explored. The challenges associated with satellite miniaturisation will be examined, along with the advantages that have contributed to the growing popularity of small satellites. Additionally, the thesis will outline the design and integration of the LEAn Femto (LEAF) Sat, a femtoSat prototype entirely constructed with Commercial Off-The-Shelf (COTS) components.