How to define text in node in a tikz matrix

Question

I have the following piece of code.

I want to add text to my nodes by simply adding the text between the ampersand symbols. What is the syntax to do this?

For example I try to add the text "John Doe" in the 1st row of the second column. The text must contain a line break between John and Doe. The usual syntax I would use would be something like:

\node[draw, align = center]{John \\ Doe};

How would do this in a matrix in which I predefined the nodes in the matrice's options?

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}
\matrix(a)[matrix of nodes , nodes in empty cells , nodes = {draw , circle , align = center} ,
column sep={1cm,between origins} , row sep = {1cm , between origins}]
{
& John \ Doe    &      & \
&        &     &\
};
\draw[->] (a-1-1) -- (a-2-1);
\end{tikzpicture}
\end{document}

Answer 1

If you give your nodes a fixed with, you can add line breaks. For example:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}
\matrix(a)[
  matrix of nodes, 
  nodes in empty cells, 
  nodes={draw, circle, align=center, text width=0.8cm},
  column sep={1.5cm, between origins}, 
  row sep={1.5cm, between origins}
]{
  & John \linebreak Doe & & \
  & & &\
};
\draw[->] (a-1-1) -- (a-2-1);
\end{tikzpicture}
\end{document}