esyN.org is a easy to use networks building tool. The user can build either Diagrams or Models. In the Diagrams tool users create graphs of interaction data, allowing interaction networks to be interactively generated and explored. In the Models tool, users create more complex graphs based on the Petri Nets formalism. Users can automatically generate and simulate a Petri Nets model based on their network. For both tools, interaction data is automatically retrieved using InterMine. As a web tool, esyN is also designed to facilitate collaboration on network models and data publication.