\documentclass{article}

\newenvironment{foo}{==[}{]==}

\begin{document}

This document contains all sorts of layouts we are supposed to
support, along with weird nestings.

At time you will see that I use subsubsections in weird places. The
intent is just to make sure that I can include a macro-type layout
everyzhere it makes sense.

A normal paragraph
\begin{equation}
x = \sin y
\end{equation}
with maths inside it.

\begin{quote}
An environment...

... with two paragraphs
\end{quote}

\begin{foo}
an unknown environment
\end{foo}


\section{A section}

\section[Hello!]{A section with optional argument}

\begin{quote}
An environment
\end{quote}

\section*{A starred section}

\begin{figure}
\caption{A figure}
\end{figure}

A paragraph\footnote{hello} with a footnote and another
one\footnote{hello

there} with several paragraphs

some ERT \vspace{1cm} aa

and another paragraph

\begin{center}
Some centered stuff (does not work)
\end{center}

\begin{quotation}
An environment

\subsubsection*{with a command inside it}
\end{quotation}

\begin{quotation}
Another environment

\begin{quotation}
With another one inside it (with same layout)

[this one even has several paragraphs!]
\end{quotation}

\end{quotation}

We can also nest enumerations

\begin{enumerate}
\item Item1
\begin{enumerate}
\item Item1.a

\item Item1.b (there is  a paragraph break in front of this)
\begin{itemize}
\item Item1.b.*
\item Item1.b.*
\end{itemize}
\end{enumerate}
\item Item2
\end{enumerate}

Let's see what happens when normal paragraphs are inserted in lists:

\begin{itemize}
\item the first item

with some explanatory text under it

and a second paragraph for good measure

\subsubsection*{we can even have one as a subsubsection}

\item the second item

\item the third item

\subsubsection*{and a sssection heading inside it (why not?)}
\end{itemize}

What else? Well, we have descriptions:
\begin{description}
\item[A] first item
\item[B] second one
\end{description}

or even bibliography
\begin{thebibliography}{9}
\bibitem{FOO} Edward Bar. \emph{The Foo Book}. (1999)
\end{thebibliography}

\end{document}