This book explores the critical need for a comprehensive census of supermassive black holes in the local universe, particularly within low mass galaxies. Supermassive black holes play a crucial role in the co-evolution of active galactic nuclei (AGN) and their host galaxies. To uncover these elusive entities, infrared selection criteria, such as the 3.4]- 4.6] m (W1-W2) color, offer a valuable method for detecting obscured AGN...