Causal loop diagrams are a systems thinking method used to qualitatively conceptualize the internal structure of a system. They focus on visualizing mental models and facilitating consensus building through identifying key variables and causal relationships. Causal loop diagrams indicate the sign and direction of causality and type of feedback in the system. They are used to develop qualitative understanding as part of system dynamics modeling approaches but are not used for simulation. Developing causal loop diagrams is an iterative participatory process involving field studies, identification of variables and linkages, and group model building.