This chapter concerns energy storage technologies. It firstly outlines two popular storage technologies, batteries and supercapacitors, while their working principles are revealed. The key issues of these two technologies, such as costs, key types, capacities, etc., are also discussed. Afterwards, a hybrid electrical energy storage (HEES) system consisting of both technologies are demonstrated where the electrical circuit is illustrated. The design of the system aims to demonstrate different characteristics of these two technologies via their charging and discharging process. A test rig is explained in detail while other components, including a load bank, an inverter, a data acquisition subsystem (both the hardware and the software) are also clarified. The experimental results are illustrated and analyzed thereafter. Also, this chapter presents several other promising technologies where their key features, pros and cons, and core applications are pointedly reviewed. The concerned storage technologies include photovoltaic (PV) systems, pumped hydro-energy storage (PHES), superconducting magnetic energy storage (SMES), gas, and other alternatives sources. The authors provide the readers with a brief insight of various energy storage technologies and the inspiration of developing a low-cost, accessible energy storage system for the reader's own purposes.