The parent of the transform.

Changing the parent will modify the parent-relative position, scale and rotation but keep the world space position, rotation and scale the same.

	// Makes the camera follow this object by
	// making it a child of this transform.
	// Get the transform of the camera
	var cameraTransform = Camera.main.transform; 	
	// make it a child of the current object
	cameraTransform.parent = transform; 
	// place it behind the current object
	cameraTransform.localPosition = -Vector3.forward * 5;
	
	// make it point towards the object
	cameraTransform.LookAt(transform);

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public Transform cameraTransform = Camera.main.transform;
    void Example() {
        cameraTransform.parent = transform;
        cameraTransform.localPosition = -Vector3.forward * 5;
        cameraTransform.LookAt(transform);
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public cameraTransform as Transform = Camera.main.transform

	def Example() as void:
		cameraTransform.parent = transform
		cameraTransform.localPosition = ((-Vector3.forward) * 5)
		cameraTransform.LookAt(transform)

Another example:

	// Detaches the transform from its parent.
	transform.parent = null;

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        transform.parent = null;
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		transform.parent = null