Tcolorboxes side by side [closed]

Question

I want to put to tcolorboxes side by side in a beamer document. I am using tcbraster to split the page in two. However, the two tcolorboxes are placed one below the other and not side by side. Strangely I manage to do what I want for the boxes "Introduction" and "Significance" but not for the "Cells" and "Demes" boxes in the attached image.

What am I doing wrong?

\documentclass{beamer}
\usepackage[size=a2,orientation=portrait,scale=1.3]{beamerposter}
\setbeamersize{text margin left=5mm,text margin right=5mm} 
\RequirePackage{enumitem}
\RequirePackage[normalem]{ulem}
\RequirePackage{etoolbox}
\usepackage[skins,most]{tcolorbox}
\tcbuselibrary{skins,raster}
\usepackage{adjustbox}
\newtcolorbox{mybox}[1]{colback=white,colframe=ICOrange, coltext=ICDeepBlue, arc=3mm, title=#1}

\newtcolorbox{ghostbox}[1][]{%
  colback=white,
  colframe=white,
  coltext=ICDeepBlue, 
  #1%
}

\usepackage{graphicx}
\usepackage{caption}
\graphicspath{ {./images/} }

\begin{document}

\begin{frame}[fragile=singleslide,t]\centering

 \maketitle

\begin{mybox}{Introduction}
\begin{tcbraster}[raster columns=2]

\begin{ghostbox}

\begin{itemize}
    \item For the principle of competitive-exclusion...
    \item Plankton ...
     \item Biophysical models have been recently...
    \item Spatial heterogeneity...
\end{itemize}
\end{ghostbox}

\begin{mybox}{Significance: Modelling Plankton Biodiversity}
\begin{figure}
    \includegraphics[width=\hsize]{significance.pdf}
\end{figure}
\end{mybox}
\end{tcbraster}

\begin{mybox}{Research Questions:}
   \begin{itemize}
    \item \textbf{How can microbial coexistence emerge in a resource-limited ecosystem ?}
    \item \textbf{Can spatial heterogeneity in the plankton structure account for emergence of coexistence ?}
    \end{itemize}
\end{mybox}

\end{mybox}


\begin{mybox}{Methods}

\begin{itemize}
    \item Investigate a biophysical model and implement a computer simulation in MATLAB.
    \item  Assume ...
\end{itemize}

\begin{tcbraster}[raster column skip=0.1\columnwidth]
\begin{mybox}{Cells}

 \begin{itemize}
   \item Every species occupies point in the space of resource consumption
\end{itemize}   

\begin{figure}
    \includegraphics[width=\hsize]{respace.pdf}
\end{figure}

\begin{itemize}
     \item Every species, $\sigma$ ...
     \item To account for trade-offs...
     \item Monod function: $r_i(c_i) = \frac{c_i}{k_i + c_i}$
\end{itemize}
\end{mybox}

\begin{mybox}{Demes}
   \begin{figure}
        \includegraphics[width=\hsize]{demes.pdf}
    \end{figure}

  \begin{itemize}
    \item The ecosystem...
    \item Nutrients...
    \item Nutrients...
    \end{itemize}

\end{mybox}
\end{tcbraster}
\end{mybox}
\end{frame}
\end{document}

Answer 1

Your problem of two side by side tcolorboxes can be reduced to the following MWE. The first frame contains the reduced MWE. In the second frame, I have removed the blank line between the two boxes. If you want the boxes to be top aligned instead of vertically centere, you can add the raster valign=top option as shown in the third frame:

\documentclass{beamer}
\usepackage[size=a2,orientation=portrait,scale=1.3]{beamerposter}
\setbeamersize{text margin left=5mm,text margin right=5mm} 
\usepackage[skins,most]{tcolorbox}
\tcbuselibrary{skins,raster}
\newtcolorbox{mybox}[1]{colback=white,colframe=orange, coltext=blue, arc=3mm, title=#1}
\usepackage{lipsum}

\begin{document}

\begin{frame}[fragile=singleslide,t]\centering
\begin{tcbraster}[raster column skip=0.1\columnwidth]
\begin{mybox}{Cells}
\lipsum[1]
\end{mybox}

\begin{mybox}{Demes}
 \lipsum[4]
\end{mybox}
\end{tcbraster}
\end{frame}

\begin{frame}[fragile=singleslide,t]\centering
\begin{tcbraster}[raster column skip=0.1\columnwidth]
\begin{mybox}{Cells}
\lipsum[1]
\end{mybox}
%
\begin{mybox}{Demes}
 \lipsum[4]
\end{mybox}
\end{tcbraster}
\end{frame}

\begin{frame}[fragile=singleslide,t]\centering
\begin{tcbraster}[raster column skip=0.1\columnwidth,raster valign=top]
\begin{mybox}{Cells}
\lipsum[1]
\end{mybox}
%
\begin{mybox}{Demes}
 \lipsum[4]
\end{mybox}
\end{tcbraster}
\end{frame}
\end{document}

Unrelated to the alignment issue: but I have removed the enumitem package as it is not compatible with the beamer documentclass.