\documentclass{minimal}
\begin{document}

Hello
\begin{centering} centered \end{centering}
world

\begin{outer}
  \begin{inner} inline environment \end{inner}
\end{outer}

\begin{tabular}{%
  ccc}
  $a$ & $b$ & $c$ \\
  $d$ & $e$ & $f$
\end{tabular}

\begin{itemize}
  \item item is indented twice
    and the next line is indented to match
\end{itemize}

\begin{description}
  \item[One] Ingeniería Electrónica ``first'';
    a couple of lines.
  \item[Doctorado] ``Generic title''
    (Author): commentaries here
\end{description}

\begin{mydocument}
  hello world
\end{mydocument}

\end{document}