The Participatory System Mapper (PRSM) is an app that makes it easy to draw networks (or 'maps') of systems, working together collaboratively.Groups of people, each using their own computer (or tablet) can collaborate in the drawing of a map using PRSM.They may be sitting around a table, discussing the map as it is created face to face, or working remotely, using video conferencing or the chat feature that is built into the app.Everyone can participate because every edit (creating nodes and links, arranging them, annotating them, and so on) is broadcast to all the other participants as the changes are made.PRSM runs in a web browser on a desktop PC or a tablet.When you start PRSM in your browser, a 'room' is created for you in which to draw your network. You can add other users to this room to share the work. Only those with access to the room can see what is being created.What can you map?The network or map can be anything that has items (or 'factors' or 'nodes') connected by links (or ‘edges'):People (the nodes) connected by knowing each otherFactors or variables causing (the links) changes in other factorsSwitches connected by wiresComputers connected by network linksTheories expressed as variables and relationships between themCompany boards of directors (the nodes) and the directors that sit on more than one board (the links)Twitter hashtags (the nodes) included together on posts (the links)Scientists (the nodes) co-authoring papers (the links)… and anything else that has items and links between the items.In addition to the 'map' view, PRSM will also show a data view: a spreadsheet with one sheet for all the factors and and another for all the links. Each row describes a factor or link, and these can be edited from the data view as well as from the map view. The data view also shows some network statistics (degree, betweenness centrality etc.) and this view can be used to assign values to factors for analysis.