matrix in \node tikzplot
\documentclass[tikz,border=2]{standalone} \usepackage{amsmath} \usepackage{pgfplots} \usetikzlibrary{shapes,snakes,calc} \tikzstyle{connector} = [->,thick] \newsavebox\myboxa \newsavebox\myboxb \savebox\myboxa{% \begin{tikzpicture} \begin{axis}[ axis lines=middle, width=4cm, ] \addplot coordinates {(0,0) (2,-3) (4,5)}; \end{axis} \end{tikzpicture}% } \savebox\myboxb{% \begin{tikzpicture} \begin{axis}[ axis lines=middle, width=4cm ] \addplot+[no marks] {x^2}; \end{axis} \end{tikzpicture}% } \begin{document} \begin{tikzpicture}[x=3in,y=2in] \tikzstyle{ann} = [draw=none,fill=none,right] \matrix[nodes={draw, thick, fill=none}, row sep=0.3cm,column sep=0.5cm] { \node[draw=none,fill=none,label={below:$\mathbf{u}$}] (N1) {\usebox\myboxa}; & \node[rectangle, minimum height=0.5in, minimum width = 0.75in] (N2) {Center}; & \node[draw=none,label={below:$\mathbf{y}$}] (N3) {\usebox\myboxb};\\ }; \draw [connector] (N1) -- node {} (N2); \draw [connector] (N2) -- node {} (N3); \end{tikzpicture} \end{document}
