Latex: how to break the line in multirow inside the tabular

p column and \parbox also works:

\usepackage{multirow}

\begin{document}
\begin{center}
\begin{tabular}{|p{1.5cm}|l|l|l|l|l|}
    \hline
    \multirow{2}{*}{\parbox{1.5cm}{Long text to break}}
    & Thing  & \multicolumn{2}{|c|}{Thing 2} & \multicolumn{2}{|c|}{Thing 3} \\
    \cline{2-6}
    & sth 1 & sth 1 & sth 2 & sth 1  & sth 2 \\ 
    \hline
    \hline
\end{tabular}
\end{center}
\end{document}