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