The year 2020 marks the 100-year anniversary of Conrad Schlumberger’s publication on electrical methods, a document that serves as the foundation of modern-day resistivity and induced polarization methods. These methods are now two of the most widely used geophysical techniques for probing the near-surface (upper few hundred metres of the Earth’s crust). Although originally developed for hydrocarbon and mineral exploration, their popularity in near-surface applications grew rapidly from the widespread recognition that subsurface electrical properties are often well correlated to physical and chemical properties of fluids within the pore space (e.g. saturation, salinity) and lithological characteristics (e.g. porosity, clay content) needed to understand a wide range of near-surface properties and processes.