# Using Base Nodes to Lay Out SpriteKit Content

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Use nonvisual nodes to define the layout of a scene.

### Overview

Each onscreen element in SpriteKit is referred to as a node. Nodes are either visual elements or containers of other nodes. You set up the appearance of a SpriteKit scene by adding nodes alongside and on top of each other in a hierarchical form. Collectively, this structure is referred to as the node tree or the node hierarchy.


These are the basic nonvisual nodes in SpriteKit:

- `SKNode` is a container node. It doesn't render any content of its own, but works as a layout tool for its child nodes.
- `SKReferenceNode` doesn't define content of its own, but refers to another node or archived file that does.
- `SKCameraNode` defines point of view within a scene. Its inverse scale is applied to all nodes in the hierarchy except for its children. Use the children of SKCameraNode for UI elements that should be unaffected by zoom level.

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