Electrokinetic measurements provide a versatile tool for analyzing the charge and structure of soft biopolymer films in contact with aqueous solutions. Recent progress was achieved in interpreting the electrokinetics of complex systems by the development of sophisticated theories on the electrohydrodynamics of diffuse soft interfaces, and with merging of experimental techniques for the concomitant determination of surface conductivity and film swelling. The fruitful options arising from these various developments are illustrated here with selected case studies. In particular, we provide insights into the experimental strategies and theoretical procedures for investigating the interrelations between the electric charging and structure of stimuli-responsive coatings, and for evaluating the key ionization characteristics, composition, and cross-linking degree of biohybrid hydrogels. Finally, we demonstrate the suitability of combined electrokinetic and FRAP measurements to understand the variations in phospholipid bilayers fluidity through interactions with electrolyte ions. These examples cover only a small range of biomaterials and processes that can be studied by means of electrokinetics. By way of further illustration, and when combined with other analytical methods such as reflectrometric interference spectroscopy,^58,59 reflectometry⁶⁰ or Fourier transform infrared spectroscopy, the methodology outlined here enables the in situ investigation of adsorption-desorption processes and the analysis of the impact of charge on the secondary structure of biopolymers at interfaces. Future developments will include the analysis of electrokinetics and surface conductivity of soft films under dynamic ion-transport conditions. Such measurements could extend our understanding on the binding and release of charged analytes, e.g., proteins, nanoparticles or heavy metal ions, to/from soft polymer materials. With the increasing complexity of the systems studied, the field would also benefit from molecular approaches that take into account ion-specific characteristics, spatial location, and chemical environment of ionisable groups within the film and local fluctuation of polymer chains.