Why am I getting a Null Reference Exception error?

New to this scene and I’m following a tutorial, but I can’t figure this out. The error I’m getting is:
“NullReferenceException: Object reference not set to an instance of an object
Player.Start () (at Assets/Scripts/Player.cs:13)”

Edit: I’m attaching the Stats.cs to a healthbar image if that helps. Trying to get the fillAmount to match the percentage of how much health the player has.

Here’s Player.cs:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Player : Character {
	private Stats Health;
	private float initHealth = 100;


	// Use this for initialization
	protected override void Start () {

		Health.Initialize (initHealth, initHealth);

		base.Start ();
	}
	
	// Update is called once per frame
	protected override void Update () {

		base.Update ();

	}
}

And Stats.cs:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Stats : MonoBehaviour {

	private Image content;

	private float currentFill;

	private float maxValue;

	public float MaxValue { get; set; }

	private float currentValue;

	public float CurrentValue {
		get {
			return currentValue;
		}
		set {
			if (value > MaxValue) {
				currentValue = MaxValue;
			} else if (value < MaxValue) {
				currentValue = 0;
			} else {
				currentValue = value;
			}
			currentFill = currentValue / MaxValue;
		}
	}

	// Use this for initialization
	void Start () {

		content = GetComponent<Image>();

	}
	
	// Update is called once per frame
	void Update () {
		Debug.Log (CurrentValue);
		content.fillAmount = currentFill;

	}

	public void Initialize (float currentValue, float maxValue){
		CurrentValue = currentValue;
		MaxValue = maxValue;
	}

}

Inside of the Start method, Health is not set to a reference but you’re attempting to use it: Health.Initialize(float, float) . You need to set a reference to Health first, then you can use its public fields, properties, methods, etc…