The concept of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) as sustainable, clean, reliable and cost-efficient power sources has come a long way since their first discovery in 2006 and 2012 respectively. A significant amount of research has been conducted to improve the performance of nanogenerators for its successful implementation in Internet of Things, wearable electronics and self-powered systems. Here, this paper reviews the recent advancements in materials and their output parameters along with their specialties based on experimental and theoretical studies in the literatures. Basic working modes of the triboelectric nanogenerator are explained in detail and the general procedure to synthesize, measure and characterize a nanogenerator is introduced in a straightforward structure.