\begin{itemize}

\item[$\blacktriangleright$] The major idea is...
\begin{itemize}
\item[$\bullet$] hhhh
\item[$\bullet$] hhhh
\item[$\bullet$] hhhh
\end{itemize}

\item[$\blacktriangleright$] The major idea is...
\begin{itemize}
\item[$\bullet$] hhhh
\item[$\bullet$] hhhh
\item[$\bullet$] hhhh
\end{itemize}

\item[$\blacktriangleright$] The major idea is...
\begin{itemize}
\item[$\bullet$] hhhh
\item[$\bullet$] hhhh
\item[$\bullet$] hhhh
\end{itemize}

\end{itemize}