NSObject is the root class of most Objective-C class hierarchies.

CAAnimation is an abstract animation class.

CAAnimationGroup allows multiple animations to be grouped and run concurrently.

CAPropertyAnimation is an abstract subclass of CAAnimation for creating animations that manipulate the value of layer properties.

CABasicAnimation provides basic, single-keyframe animation capabilities for a layer property.

The CAKeyframeAnimation class provides keyframe animation capabilities for a layer object.

The CATransition class implements transition animations for a layer.

A CADisplayLink object is a timer object that allows your application to synchronize its drawing to the refresh rate of the display.

The CAEmitterCell class represents one source of particles being emitted by a CAEmitterLayer object.

The CALayer class manages image-based content and allows you to perform animations on that content.

The CAEAGLLayer class supports drawing OpenGL content in iPhone applications.

The CAEmitterLayer class provides a particle emitter system for Core Animation.

The CAGradientLayer class draws a color gradient over its background color, filling the shape of the layer (including rounded corners)

A CAMetalLayer object is a Core Animation layer that manages a pool of Metal textures for rendering its content using Metal.

The CAReplicatorLayer class creates a specified number of copies of its sublayers (the source layer), each copy potentially having geometric, temporal and color transformations applied to it.

The CAScrollLayer class is a subclass of CALayer that simplifies displaying a portion of a layer.

The CAShapeLayer class draws a cubic Bezier spline in its coordinate space.

The CATextLayer provides simple text layout and rendering of plain or attributed strings.

CATiledLayer is a subclass of CALayer providing a way to asynchronously provide tiles of the layer's content, potentially cached at multiple levels of detail.

CATransformLayer objects are used to create true 3D layer hierarchies, rather than the flattened hierarchy rendering model used by other CALayer classes.

CAMediaTimingFunction represents one segment of a function that defines the pacing of an animation as a timing curve.

CATransaction is the Core Animation mechanism for batching multiple layer-tree operations into atomic updates to the render tree.

The CAValueFunction.h class provides a more flexible means of applying functions to property values during animation.