\documentclass{minimal}
\begin{document}

\begin{tabular}{cc}
  \begin{tabular}{c}
    Cell 1
  \end{tabular} &
  \begin{tabular}{c}
    Cell 2
  \end{tabular}
\end{tabular}

\begin{equation}
  \begin{aligned}
    1 &
      & 2 \\
    3 &
      & 4 \\
  \end{aligned}
\end{equation}

\begin{environ*}
  A &= 10
  \\&= \command{
    something
  }
  \\&= 20
\end{environ*}

\end{document}