joint.dia.Paper is the view for the `joint.dia.Graph` model. It inherits from the Backbone View. When a paper is associated with a graph, the paper makes sure that all the cells added to the graph are automatically rendered.

    var graph = new joint.dia.Graph
    var paper = new joint.dia.Paper({
        el: $('#paper'),
        width: 600,
        height: 400,
        gridSize: 10,
        model: graph
    });

    var rect = new joint.shapes.basic.Rect({
        position: { x: 50, y: 70 },
        size: { width: 100, height: 40 }
    });

    graph.addCell(rect);

Paper automatically handles this change and renders the rectangle to the SVG document that it internally holds.