Quaternion.FromToRotation
static function FromToRotation(fromDirection: Vector3, toDirection: Vector3): Quaternion;
static Quaternion FromToRotation(Vector3 fromDirection, Vector3 toDirection);
static def FromToRotation(fromDirection as Vector3, toDirection as Vector3) as Quaternion
Description

Creates a rotation which rotates from fromDirection to toDirection.

Usually you use this to rotate a transform so that one of its axes eg. the y-axis - follows a target direction toDirection in world space.
	// Sets the rotation so that the transform's y-axis goes along the z-axis

transform.rotation = Quaternion.FromToRotation (Vector3.up, transform.forward);
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        transform.rotation = Quaternion.FromToRotation(Vector3.up, transform.forward);
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		transform.rotation = Quaternion.FromToRotation(Vector3.up, transform.forward)