# Multi-column subfloats with subfig

I have to use subfig instead of subcaption because the style I have to use redefines the look of captions and I can't change that. Given this constraint, how do I use multicol to make multiple-columns subfloats?

The problem is that this doesn't work:

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[caption=false]{subfig}
\usepackage{multicol}

\begin{document}

\begin{figure}
\subfloat[inner caption]{
\begin{multicols}{2}
\end{multicols}
}
\caption{outer caption}
\end{figure}
\end{document}


since it results in

 ! LaTeX Error: Something's wrong--perhaps a missing \item.


(BTW, "something's wrong" is the stupidest error message I've ever seen...)

My ultimate goal is to put two bussproof proof trees side-by-side, and then more, wider proof trees in single column below it; all in the same single subfloat.

• @Zarko: Two pictures next to each other on one line, then a third picture in a second line, and these three together should share one sub-caption; then more pictures with a second shared sub-caption; then some more, and so on. And then the whole thing would also have its own caption. Jul 30 '16 at 10:24

What about using minipage inside the subfigure?

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[caption=false]{subfig}
\usepackage{multicol}
\usepackage{lipsum}

\begin{document}

\begin{figure}
\subfloat[inner caption]{
\begin{minipage}{\textwidth}
\begin{multicols}{2}
\lipsum[1]
\end{multicols}
\end{minipage}
}

\subfloat[inner caption2]{
\begin{minipage}{\textwidth}
\begin{multicols}{2}
\lipsum[2]
\end{multicols}
\end{minipage}
}
\caption{outer caption}
\end{figure}
\end{document}