Harvesting ambient energy, as an alternative power source, tackles the increasing demand for future energy-efficient autonomous sensor systems, especially for applications requiring miniaturisation and distributed sensing such Wireless Sensors Network and Internet-of-Things. A functional energy harvesting system requires addressing simultaneously all the components of the system: the harvester device, the energy storage and the powering management circuits. These components are described through examples of miniaturized kinetic-based harvesting systems for low-power applications with focus on energy harvester, piezoelectric and electromagnetic, respectively.