Matrix of nodes with multiple lines

I am working with a binomial tree as shown below (code at end of post).

How can I make a new line within each node? I would like to add a second number below each of the numbers in the node.

\documentclass{article}
\usepackage{amssymb,mathtools}
\usepackage{tikz}
\usetikzlibrary{matrix,arrows}

\begin{document}

\begin{tikzpicture}[>=stealth,sloped]
\matrix (tree) [%
matrix of math nodes,
minimum size=1cm,
column sep=2.5cm,
row sep=0.4cm,
column 1/.style={nodes={draw,rounded corners,
top color=white, bottom color=blue!20}},
column 2/.style={nodes={draw,fill=green!30,rounded corners}},]
{
& 2800 \\
2500 &  \\
& 2700 \\
};

\draw[->] (tree-2-1) -- (tree-1-2) node [midway,above] {$p$};
\draw[->] (tree-2-1) -- (tree-3-2) node [midway,below] {$1-p$};

\end{tikzpicture}

\end{document}


Look at section 57.2 End-of-Lines and End-of-Row Characters in Matrices of Nodes in pgfmanual.

In a matrix of nodes (not matrix of math nodes although I don't know why) you can add text width and align options and place \\ in node contents to break lines. Multiline node contents must be inside braces { ... \\ ... }.

\documentclass{article}
\usepackage{amssymb,mathtools}
\usepackage{tikz}
\usetikzlibrary{matrix,arrows}

\begin{document}

\begin{tikzpicture}[>=stealth,sloped]
\matrix (tree) [%
matrix of nodes,
minimum size=1cm,
column sep=2.5cm,
row sep=0.4cm,
column 1/.style={nodes={draw,rounded corners,
top color=white, bottom color=blue!20}},
column 2/.style={nodes={draw,fill=green!30,rounded corners, text width=1cm, align=center}},
]
{
& {2800 \\ 2700} \\
2500 &  \\
& 2700 \\
};

\draw[->] (tree-2-1) -- (tree-1-2) node [midway,above] {$p$};
\draw[->] (tree-2-1) -- (tree-3-2) node [midway,below] {$1-p$};

\end{tikzpicture}

\end{document}