diff --git a/default.nix b/default.nix
index 83685bd5153e112e55cacc8d73f3b94c8f5f3ce1..cc5fe35a763a5084cc9d779712dc96000092b9d6 100644
--- a/default.nix
+++ b/default.nix
@@ -37,9 +37,9 @@ stdenv.mkDerivation rec {
     cp paper.pdf $out
     '';
   buildInputs = inputs;
-  shell = mkShell {
-    buildInputs = inputs;
-    shellHook = "ls | entr make";
-  };
+    shell = mkShell {
+      buildInputs = inputs;
+      shellHook = "ls | entr make";
+    };
 
 }
diff --git a/slides.pdf b/slides.pdf
index ff575bc93791698a559f3897b7df5406f191307d..efc0767da3d39f977a4ac5712f9b7604fcda1d2c 100644
Binary files a/slides.pdf and b/slides.pdf differ
diff --git a/slides.tex b/slides.tex
index 528fd1c7bdd319f13eb5e0baca819ca8190bac96..0d1f6b7d0e637045c6d389f8c36aa7404b5d205d 100644
--- a/slides.tex
+++ b/slides.tex
@@ -437,7 +437,7 @@ The result of the build action is automatically placed into the nix store.
 
   \vspace{1em}
 
-  NixPkgs contains the derivations of all application (and libraries) \emph{officialy} available with Nix.
+  NixPkgs contains the derivations of all application (and libraries) \emph{officially} available with Nix.
 \end{frame}
 
 
@@ -451,7 +451,9 @@ The result of the build action is automatically placed into the nix store.
   A \textbf{channel} is link to  branch of NixPkgs tested with continuous integration.
 \end{tcolorbox}
 
+  \vspace{1em}
 
+  Channels are useful to downloaded latest version of a software.
 
   \vspace{1em}
 
@@ -464,14 +466,43 @@ The result of the build action is automatically placed into the nix store.
 
   \only<2>{
 
-\begin{tcolorbox}[colframe=red!17,colback=red!10,coltext=black]
+\begin{tcolorbox}[colframe=red!37,colback=red!10,coltext=black]
   \center
     Channels are not fully reproducible, as they are subject to updates.
 \end{tcolorbox}
+  \vspace{1em}
+  As experimenters,  we will use another mechanism called pinning.
   }
 
 \end{frame}
 
+\begin{frame}{Key points}
+
+  \begin{enumerate}
+  \item Applies functional paradigm to package management system.
+  \item Packages are derivations, written in Nix lang.
+  \item The list of existing packages are into NixPkgs repository.
+  \item All build package are located into the store.
+  \end{enumerate}
+
+\end{frame}
+
+\begin{frame}{Why it is reproducible ?}
+
+\end{frame}
+
+\begin{frame}{Nix - Command line interface}
+  How do we use Nix ?
+  \vspace{1em}
+  \begin{itemize}
+    \item \textit{nix-build} : build a derivation (that will be placed to the nix store),
+    \item \textit{nix-env} : install a package (in your current environment)
+      \note{Speak about profiles?},
+    \item \textit{nix-shell} : start a shell in the build environment of a derivation,
+    \item \textit{nix search} : Search for available packages.
+  \end{itemize}
+\end{frame}
+
 % \begin{frame}[fragile]{}
 % 
 %   A derivation is identified with a hash of its inputs (\emph{sources}, and \emph{derivations})