The list data structure in R allows the user to store homogeneous (of the same type) or heterogeneous (of different types) R objects. Therefore, a list can contain objects of any type including lists themselves.

# Code

## Method 1

In the code snippet below, two lists are created and then combined into another list. The output shows that `animals` is a list containing two elements, `mammals` is a list containing three elements, ​and `amphibians` is a list containing one element. 


# Creating a list
mammals <- list("cat", "dog", "bear")
# Creating another list
amphibians <- list("frog")
# Creating a list of lists
animals <- list(mammals, amphibians)
# Printing the list
cat(str(animals))

## Method 2

The lists that are to be contained in another list can be created inline. Moreover, titles can be assigned to the list elements, as shown below. Note that `mammals` and `amphibians` are titles of the lists created inline.

# Creating a list
# Creating a list of lists
animals <- list(mammals = list("cat", "dog", "bear"), amphibians = list("frog"))
# Printing the list
cat(str(animals))

How to create a list of lists in R

Store homogeneous or heterogeneous objects in R lists, including inline or combined lists with titled elements.