1 \documentclass{article}

     2 \begin{document}

     3 This is my simple document with nested lists. 

     4 \begin{enumerate}

     5 \item First Enumerated Item. 

     6 \item Second Enumerated Item. 

     7 \item Third Enumerated Item. 

     8   \begin{itemize}

     9   \item First Item.

    10   \item Second Item.

    11   \item Third Item.

    12     \begin{itemize}

    13     \item First Sub-Item.

    14     \item Second Sub-Item.

    15     \item Third Sub-Item.

    16     \item Fourth Sub-Item.

    17     \end{itemize}

    18 \end{enumerate}

    19 \end{document}