\documentclass{article}
\usepackage{graphics}
% Various wierdnesses about vertical mode, centering and such.
\begin{document}

\section{Nesting hbox \& vbox}
\hbox{a b c d}

\hbox{\hbox{a}\hbox{b}\hbox{c}\hbox{d}}

\hbox{\vbox{a}\vbox{b}\vbox{c}\vbox{d}}

\vbox{a b c d}

\vbox{\hbox{a}\hbox{b}\hbox{c}\hbox{d}}

\vbox{\vbox{a}\vbox{b}\vbox{c}\vbox{d}}

\hbox{\hbox{a}\hbox{b}\vbox{\hbox{a}\hbox{b}\hbox{c}\hbox{d}}\hbox{c}\hbox{d}}

\section{parbox and minipage}

\parbox{2in}{%
  \hbox{hbox1}\vbox{vbox1}\hbox{hbox2}\hbox{hbox3}\vbox{vbox2}}

\begin{minipage}{2in}
This is random text. This is random text.
This is random text. This is random text. This is random text.
\begin{itemize}
\item One
\item Two
\item Three
\end{itemize}
This is random text. This is random text.
This is random text. This is random text. This is random text.
\end{minipage}


\section{Centering}

\begin{center}
This is random text. This is random text. This is random text.
This is random text. This is random text. This is random text.
This is random text. This is random text. This is random text.
This is random text. This is random text. This is random text.
\end{center}

\begin{center}
This is random text. This is random text. This is random text.

This is random text. This is random text. This is random text.

This is random text. This is random text. This is random text.
\end{center}


\begin{center}
\includegraphics{foo.png}
\bigskip

c) Parabolic cylinder, \,$x^2 = 2pz$;\, it is a developable surface. \\
Signatures: blah $x$, $y$)
\end{center}

\begin{figure}
\begin{center}
\includegraphics{foo}
\caption{This is random text. This is random text. This is random text.}
\end{center}
\end{figure}

\begin{figure}
\begin{center}
A Figure line\\
Another Figure line\\
Yet another Figure line\\
\caption{Figure: This is a figure.} 
\end{center}
\end{figure}


\section{Graphics rescaling}
\includegraphics{foo}

\scalebox{3}[2]{\includegraphics{foo}}

\end{document}