Three-dimensional electromagnetic (EM) techniques are important and powerful tools for natural resources exploration (oil, minerals, geothermal, etc.) and geotechnical and environmental investigations because 3D imaging can provide detailed information about the subsurface. This special section is dedicated to 3D EM methods and their successful applications, aiming to present the current state of the art in theoretical developments and practical applications and to stimulate interest across a wide range of geophysicists.@en