diff --git a/slides.tex b/slides.tex
index aad9852b03e2784e006ad3134f5d55e805ced0d2..dc0f9391668aafe91ee3e6334464fc03ba4b0803 100644
--- a/slides.tex
+++ b/slides.tex
@@ -187,7 +187,7 @@ The Problem:
 
 \end{frame}
 
-\subsection{Packages}
+\subsection{Packages Example}
 
 \begin{frame}[fragile]{Package Definition Example}
   % It is a Nix attribute set describing how to build a package.
@@ -247,6 +247,20 @@ stdenv.mkDerivation {
 \end{columns}
 \end{frame}
 
+\subsection{Nix tools}
+
+\begin{frame}[fragile]{Nix Build: build packages}
+
+\vspace{1em}
+
+\includegraphics[width=1\textwidth]{./figures/nix-build.pdf}
+
+\end{frame}
+
+\begin{frame}[fragile]{Nix shell: Virtualenv on steroids}
+  \includegraphics[width=1\textwidth]{./figures/nix-shell.pdf}
+\end{frame}
+
 \subsection{NixPkgs}
 
 \begin{frame}[fragile]{Nixpkgs}
@@ -270,52 +284,35 @@ stdenv.mkDerivation {
 
 \end{frame}
 
-\subsection{Nix tools}
-
-\begin{frame}[fragile]{Nix Build: build packages}
-
-\vspace{1em}
-
-\includegraphics[width=1\textwidth]{./figures/nix-build.pdf}
-
-\end{frame}
-
-\begin{frame}[fragile]{Nix shell: Virtualenv on steroids}
-  \includegraphics[width=1\textwidth]{./figures/nix-shell.pdf}
-\end{frame}
-
-\begin{frame}[fragile]{Why it is reproducible ?}
 
+\begin{frame}[fragile]{}
+\begin{columns}
+\begin{column}{0.5\textwidth}
+Why it is reproducible ?
   \begin{itemize}
   \item Package = traceable dependencies
   \item Automated package build
   \item fixed application source
- \begin{lstlisting}[language=Nix,basicstyle=\small]
-src = fetgit {
-  url = "https://gitlab.com/me/chord.tar.gz";
-  sha256 = "1h2jgq5pspyiskffq777nhi5rf0y8h...";
-};
-  \end{lstlisting}
   \item pinned Nixpkgs
-  \begin{lstlisting}[language=Nix,basicstyle=\small]
-{
-  pkgs ? import (fetchTarball
-    "https://github.com/archive/e6b201f9b.tar.gz"
-    )
-}:
-  \end{lstlisting}
   \end{itemize}
-\end{frame}
-
-\subsection{Limitations}
-\begin{frame}[fragile]{Limitations}
+\end{column}
+\begin{column}{0.5\textwidth}  %%<--- here
+Limitations
   \begin{itemize}
     \item No kernel version control
     \item Require deterministic build process
     \item Can depends on external dependencies
   \end{itemize}
+\end{column}
+\end{columns}
+
 \end{frame}
 
+
+
+
+
+
 \begin{frame}[fragile,noframenumbering]
   \center Thanks.
 \end{frame}
@@ -488,6 +485,4 @@ pkgs.mkShell rec {
 
 \end{frame}
 
-
-
 \end{document}