Visible-light photoredox catalysis has been successfully used in the functionalization of inert C-H bonds including C(sp2 )-H bonds of arenes and C(sp3 )-H bonds of aliphatic compounds over the past decade. These transformations are typically promoted by the process of single-electron-transfer (SET) between substrates and photo-excited photocatalyst upon visible light irradiation (household bulbs or LEDs). Compared with other synthetic strategies, such as the transition-metal catalysis and traditional radical reactions, visible-light photoredox approach has distinct advantages in terms of operational simplicity and practicability. Versatile direct functionalization of inert C(sp2 )-H and C(sp3 )-H bonds including alkylation, trifluoromethylation, arylation and amidation, has been achieved using this practical strategy.