The critical features of atomic or molecular scalar fields can be captured by mapping their topography. The topography maps, viz., molecular electron density (MED) and molecular electrostatic potential (MESP), are successfully used to characterize the weak interactions that exist in systems ranging from small molecular clusters to large supramolecular systems. Topography mapping mainly involves identifying and characterizing their critical points (CPs). These CPs are extremely useful for describing the nature of weak interactions and quantifying the strength of interaction. The first part of the chapter delineates fundamental concepts related to MED and MESP. Later, the usefulness of MED and MESP analyses for understanding weak interactions is demonstrated by taking various molecular complexes.