\begin{tikzpicture}[node distance=1.2cm,>=stealth',bend
  angle=25,auto,scale=1.0,transform shape]

  \tikzstyle{place}=[circle,thick,draw=red!75,fill=red!20,minimum size=5mm]
  \tikzstyle{transition}=[rectangle,thick,draw=blue!75,fill=blue!20,minimum size=4mm]

  \tikzstyle{every label}=[black]

  \begin{scope}
    
    % Petri net A
    \node [place] (pa1) [xshift=-3.5cm]{} ;

    \node [transition] (ta1) [below of=pa1] {}
      edge [pre]  (pa1)
    ;

    %%in order to center tstart transition
    \node [place] (pa) [below of=ta1,circle,draw=white,fill=white] {};

    \node [place] (pa2) [left of=pa] {}
      edge [pre] (ta1)
    ;

    \node [place] (pa3)  [right of=pa] {}
      edge [pre] (ta1)
    ;
    \node at (pa3.west) [left] {};

    \node [transition] (ta2) [below of=pa2] {}
      edge [pre]  (pa2)
    ;

    \node [place] (pa4) [below of=ta2] {}
      edge [pre] (ta2)
    ;

    % Petri net B
    \node [place] (pb1) {};

    \node [transition] (tb1) [below of=pb1] {}
      edge [pre] (pb1)
      ;
    \node at (tb1.east) [right] {};

    %%in order to center tstart transition
    \node [place] (pp) [below of=tb1,circle,draw=white,fill=white] {};
    \node [place] (pb2) [left of=pp] {}
      edge [pre] (tb1)
    ;
    \node [place] (pb3) [right of=pp] {}
      edge [pre] (tb1)
    ;

    \node [transition] (tb2) [below of=pb2] {}
      edge [pre]  (pb2)
      edge [pre,bend right,green!50!black,thick] (pa3)
      ;

    \node [place] (pb4) [below of=tb2] {}
      edge [pre] (tb2)
    ;

    %C, D, ...
    %(finally not invisible) nodes
    \node [place] (pi1) [right of=pb3,draw=white,fill=white] {} ;
    \node [transition] (ti) [below of=pi1,draw=blue!15,fill=blue!5] {}
      edge [pre,bend right,green!50!black,thick] (pb3)
      ;


     % last Petri net: Z
    \node [place] (pz1) [xshift=8cm] {}
    ;

    \node [transition] (tz1) [below of=pz1] {}
      edge [pre] (pz1)
      ;
    \node at (tz1.east) [right] {};

    %%in order to center tstart transition
    \node [place] (pz) [below of=tz1,circle,draw=white,fill=white] {};
    \node [place] (pz2) [left of=pz] {}
      edge [pre] (tz1)
    ;
    %(finally not invisible) nodes
    \node [place] (pi2) [left of=pz2,draw=red!15,fill=red!5] {} ;
    \node (phantom) [left of=pi2,xshift=-0.5cm] {$\cdots\cdots\cdots$};

    \node [place] (pz3) [right of=pz] {}
      edge [pre] (tz1)
    ;

    \node [transition] (tz2) [below of=pz2] {}
      edge [pre,bend right,green!50!black,thick] (pi2)
      edge [pre]  (pz2)
      ;

    \node [place] (pz4) [below of=tz2] {}
      edge [pre] (tz2)
    ;
 
 % Petri net root
    \node [place] (p1) [tokens=1,xshift=-6.5cm]{}
    ;
    
    \node [transition] (t1) [below of=p1] {}
      edge [pre]  (p1)
      edge [post,bend left,dash pattern=on 2pt off 2pt] (pa1)
      edge [post,bend left,dash pattern=on 2pt off 2pt] (pb1)
      edge [post,bend left,dash pattern=on 2pt off 2pt] (pz1)
    ;

    \node [place] (p2) [below of=t1] {}
      edge [pre] (t1)
    ;

    \node [transition] (t2) [below of=p2] {}
      edge [pre]  (p2)
      edge [pre,bend right,dash pattern=on 2pt off 2pt] (pa4)
      edge [pre,bend right,dash pattern=on 2pt off 2pt] (pb4)
      edge [pre,bend right,dash pattern=on 2pt off 2pt] (pz4)
    ;

    \node [place] (p3) [below of=t2] {}
      edge [pre] (t2)
    ;
    
  
  \end{scope}
\end{tikzpicture}
