If $S=\set{\blacksquare,\,\blacklozenge,\,\bigstar}$, $T=\set{\bigstar,\,\blacklozenge}$, $R=\set{\blacktriangle,\,\bigstar}$, then \begin{align*} T&\subseteq S & R&\not\subseteq T & \emptyset&\subseteq S \\ T&\subset S & S&\subseteq S & S&\not\subset S \end{align*}