Quaternion.FromToRotation

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.

using UnityEngine;

public class Example : MonoBehaviour
{
    void Start()
    {
        // Sets the rotation so that the transform's y-axis goes along the z-axis
        transform.rotation = Quaternion.FromToRotation(Vector3.up, transform.forward);
    }
}