This book begins with a comprehensive review of vibration energy harvesting, encompassing its theoretical foundations, methodologies, and practical applications. It then introduces a series of studies involving various X-structure configurations within distinct nonlinear frameworks. Over recent decades, energy harvesting has garnered significant research attention, driven by the objective of minimizing reliance on external power sources and maintenance in electronic systems such as wireless sensor networks. Among the various approaches, vibration-based energy harvesting has emerged as a promising solution. However, its effectiveness is constrained by the dependence of power output on the resonant frequencies of ambient vibrations, which are typically stochastic and span a broad frequency spectrum. To overcome this limitation, researchers have explored advanced materials and optimized structural designs, with particular emphasis on incorporating nonlinear dynamics to broaden the operational frequency bandwidth. This chapter reviews three principal mechanisms for converting vibrational energy into electrical energy, detailing their theoretical underpinnings, design strategies, and reported applications. It also compares the energy conversion efficiencies of these mechanisms, a critical metric for evaluating performance. Finally, the chapter addresses current challenges and outlines future directions for research in energy harvesting technologies.