Cfrgtkky

I want the nodes c and d be inside q and the position of q to be determined by p.

A second problem is, that the distance between p and q isn't correct even with on grid=false (I guess the width of p isn't available because of using fit?).

documentclass[tikz]{standalone}

usetikzlibrary{positioning,fit}



begin{document}



begin{tikzpicture}

node (a) [draw=black] {a};

node (b) [draw=black,on grid,below=of a] {long text};

node (p) [draw=black,fit={(a) (b)}] {};



node (c) [draw=red] {c};

node (d) [draw=red,below=of c] {d};

node (q) [right=of p,draw=red,fit={(c) (d)}] {};

end{tikzpicture}

end{document}

How about using a matrix?

documentclass[tikz]{standalone}

usetikzlibrary{fit,matrix}



begin{document}



begin{tikzpicture}

matrix[column sep=8mm,row sep=3mm] {

node (a) [draw=black] {a};

&

node (c) [draw=red] {c};

\

node (b) [draw=black] {long text};

&

node (d) [draw=red] {d};

\

};

node (p) [draw=black,fit={(a) (b)}] {};

node (q) [draw=red,fit={(c) (d)}] {};

end{tikzpicture}

end{document}

The advantage of using one matrix (instead of two) is that it also looks good if the vertical dimensions of the nodes vary.

documentclass[tikz]{standalone}

usetikzlibrary{fit,matrix}



begin{document}



begin{tikzpicture}

matrix[column sep=8mm,row sep=3mm,anchor=center] (mat) {

node (a) [draw=black] {a};

&

node (c) [draw=red] {c};

\

node (b) [draw=black,align=center] {long\ text};

&

node (d) [draw=red] {d};

\

};

node (p) [draw=black,fit={(a) (b) (b|-mat.south)}] {};

node (q) [draw=red,fit={(c) (d) (d|-mat.south)}] {};

end{tikzpicture}

end{document}

As in any TikZ matrix, every line, including the last one, has to be terminated by \.

marmot proposes to use a matrix, but I think two matrices are better:

documentclass[tikz]{standalone}

usetikzlibrary{positioning,matrix}



begin{document}



begin{tikzpicture}

matrix[draw, matrix of nodes, nodes=draw, row sep=3mm] (a) {

a\

long text\

};



matrix[draw=red, matrix of nodes, nodes={draw=red}, 

          right=3mm of a, row sep=3mm] (b) {

c\

dvphantom{g}\

};

end{tikzpicture}

end{document}

documentclass[tikz,margin=3mm]{standalone}

usetikzlibrary{fit, positioning}



begin{document}



begin{tikzpicture}[

node distance = 8mm and 4 mm,

every node/.style = {inner sep=1mm, minimum height=1.5em}

                    ]

node (a) [draw=black] {a};

node (b) [draw=black,below=of a] {long text};

node (p) [draw=black,fit={(a) (b)}] {};



node (c) [draw=red,right=of b.east |- a] {c};

node (d) [draw=red,below=of c] {d};

node (q) [draw=red,fit={(c) (d)}] {};%right=of p,

end{tikzpicture}

end{document}