Is it possible to make a List into another List? C#

using System.Collections.Generic;

	List<float> holdAllThreeList = new List<float>();
	List<float> listOne = new List<float>();
	List<float> listTwo = new List<float>();
	List<float> listThree = new List<float>();
	
	void Start()
	{
		holdAllThreeList.Add(listOne);
		holdAllThreeList.Add(listTwo);
		holdAllThreeList.Add(listThree);
	}

But I got 2 errors which is:

1. The best overloaded method match for `System.Collections.Generic.List<float>.Add(float)' has some invalid arguments
    
2. Argument `#1' cannot convert `System.Collections.Generic.List<float>' expression to type `float'

On line 3:

 List<float> holdAllThreeList = new List<float>();

You are setting the list to accept floats only.

When creating a list of lists you need to explicitly say it needs to be in the format of [List of floats]:

   List<List<float>> holdAllThreeList = new List<List<float>>();

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

public class asd2 : MonoBehaviour
{

    public List<float> holdAllThreeList = new List<float>();
    public List<float> listOne = new List<float>();
    public List<float> listTwo = new List<float>();
    public List<float> listThree = new List<float>();

    void Start()
    {
        StartCoroutine(AddList(listOne));
        StartCoroutine(AddList(listTwo));
        StartCoroutine(AddList(listThree));
    }


    IEnumerator AddList(List<float> list)
    {
       foreach(float i in list)
        {
            holdAllThreeList.Add(i);
        }
        yield return new WaitForEndOfFrame();
    }
}