Attaching this script to a object, the object survives in all scenes. (For Unity3d)

DontDestroyObject.cs

using UnityEngine;
using System.Collections;

public class DontDestroyObject : MonoBehaviour
{
	static DontDestroyObject instance;

	void Awake ()
	{
		if (!instance) {
			instance = this;
			DontDestroyOnLoad (gameObject);
		} else {
			Destroy (gameObject);
		}
	}	
}