<ReactDataGrid /> offers support for hierarchical data - configure a treeColumn and make your dataSource items have a nodes array with child records.treeColumn specifies which column will render the tree collapse/expand/loading icons (the icon can be further configured via renderNodeTool prop).<ReactDataGrid /> as a tree, we refer to rows as nodes.expandedNodes prop (this prop is controlled, see defaultExpandedNodes for uncontrolled version). The value of this prop should be an object - the keys in this object are the ids of the expanded nodes, while the value for each key should be true.<ReactDataGrid /> will assign a unique id (see idProperty) to all nodes based on the path from the root node to the respective node. This id value is built by joining all the parent ids using the / character (as defined by nodePathSeparator prop). So, for example, expandedNodes could look like this for a grid: expandedNodes={ 1: true, 3: true, '3/1': true', '3/2/1': true }.<ReactDataGrid /> is not compatible with grouping rows.<ReactDataGrid />.<ReactDataGrid /> is understanding async and leaf nodes.nodes property defined (so if nodes !== undefined) it is not a leaf node.nodes === undefined (the nodes property name is configurable via nodesProperty).nodes property of a tree node is an array, the node is a parent node (even if nodes.length === 0) and also a synchronous node.nodes property is equal to null. In this case, when the user tries to expand the async node, the <ReactDataGrid /> calls the loadNode({ node, nodeProps }) function prop to load the node children. Alternatively, you could specify loadNodeOnce({ node, nodeProps }) to have the grid load the node children and cache them for future re-use.loadNode({ node, nodeProps }) and loadNodeOnce({ node, nodeProps }) should either return an array (or undefined) or a Promise that resolves to an array (or undefined).isNodeAsync({ node, nodeProps }) and isNodeLeaf({ node, nodeProps }) props respectively.4.0.26 introduced stickyTreeNodestreeNestingSize.onExpandedNodesChange({ expandedNodes }) function prop is called. Before this function being called, you can cancel the expand by returning false from onNodeExpand or from onNodeExpandChange (called in this order). Cancelling a node collapse can be done by returning false from onNodeCollapse or from onNodeExpandChange (called in this order).expandedNodes, don't forget to update the prop in response to onExpandedNodesChange being called.