Welcome to the Laboratory of Complex Systems (Laboratorio de Sistemas Complejos, LSC)! We are part of the Department of Fundamental Physics and the Fluids and Soft Matter Group at UNED (Universidad Nacional de Educación a Distancia) in Madrid, Spain. Our research interests lie at the intersection of applied physics, fluid mechanics, and materials science, with an emphasis on the study of soft material interfaces. Soft material interfaces dictate the behavior of biological, industrial, and technological systems featuring large surface area–to–volume ratios, such as microliter-scale configurations (e.g., foams, emulsions), thin liquid films (e.g., coatings, the human tear film, mucosal linings), and branched, hierarchical structures (e.g., the human lung). Our lab focuses on elucidating the structure-function-property relationship of different soft material interfaces, in order to understand how they respond to flow and deformation, control the stability and behavior of interface-dominated systems, and design materials with desired properties. To this end, we design and build custom mechanical devices (interfacial rheometers) and complementary numerical flow-field based data analysis routines for determining the mechanical, thermodynamic, and transport properties of fluid-fluid soft material interfaces. Our interfacial rheometers have been predominantly used to interrogate physiological and biologically inspired interfaces, such as those composed of fatty acids, lipids, and bio-surfactants.