diff --git a/flake.nix b/flake.nix
index 1e5d2a4..704a7ee 100644
--- a/flake.nix
+++ b/flake.nix
@@ -50,26 +50,28 @@
           '';
         };
 
-        fg42 = pkgs.callPackage ./nix/fg42 {
+        app = pkgs.callPackage ./nix/fg42 {
           inherit nixpkgs;
           extraPackages = {
             noether = inputs.noether.outputs.packages.${system}.default;
           };
         };
 
-        fg42-wm = pkgs.callPackage ./nix/fg42 {
-          inherit nixpkgs;
-          modules = [
-            ./nix/modules/editor
-            ./nix/modules/elisp
-            ./nix/modules/graphics
-            ./nix/modules/noether
-            ./nix/modules/wm
-          ];
-          extraPackages = {
-            noether = inputs.noether.outputs.packages.${system}.default;
-          };
-        };
+        fg42 = app.drv;
+        fg42-wm = pkgs.callPackage ./nix/fg42
+          {
+            inherit nixpkgs;
+            modules = [
+              ./nix/modules/editor
+              ./nix/modules/elisp
+              ./nix/modules/graphics
+              ./nix/modules/noether
+              ./nix/modules/wm
+            ];
+            extraPackages = {
+              noether = inputs.noether.outputs.packages.${system}.default;
+            };
+          }.drv;
 
         run-test-wm = pkgs.writeShellApplication {
           name = "run-test-wm";
@@ -82,7 +84,7 @@
 
       in
       {
-        packages = {
+        packages = app.emacsPkgs // {
           default = fg42;
           wm = fg42-wm;
         };
diff --git a/nix/fg42/derivation.nix b/nix/fg42/derivation.nix
index 324db85..81f4135 100644
--- a/nix/fg42/derivation.nix
+++ b/nix/fg42/derivation.nix
@@ -64,151 +64,163 @@ let
   };
 
 in
-stdenv.mkDerivation rec {
-  inherit version src pname;
+{
+  emacsPkgs = (emacsPackagesFor emacs);
+  drv =
+    stdenv.mkDerivation rec {
+      inherit version src pname;
+
+      buildPhase = ''
+        runHook preBuild
+
+        # =============================
+        # Building FG42 itself
+        # =============================
+        LISPDIR=$out/share/fg42/
+        STARTUP_FILE=$LISPDIR/lisp/fg42_init.el
+
+        mkdir -p $out/bin
+        mkdir -p $out/share/applications/
+
+        install -d $LISPDIR
+
+        mkdir -p $LISPDIR/lisp
+        cp -rv ${src}/lisp/build.el $LISPDIR/lisp
+
+        cp -rv ${src}/share $out/
+        cp -rv ${src}/snippets $LISPDIR/snippets
+        cp "${fontsConf}" $LISPDIR/fonts.conf
+        cp "${configFile}" $LISPDIR/config.json
+
+        export FONTCONFIG_FILE="$LISPDIR/fonts.conf"
+        chmod 755 $LISPDIR -R
+
+        emacs --batch -l $LISPDIR/lisp/build.el $LISPDIR/config.json $STARTUP_FILE
+        #emacs -Q --batch -l package --eval "(package-generate-autoloads \"fg42_init" \"$LISPDIR\")"
+        emacs --batch -l loaddefs-gen -f loaddefs-generate-batch $LISPDIR/lisp/ $LISPDIR/lisp/ ${emacsBundle}
+        cd $LISPDIR
+        #compile stuff
+        cd -
+
+        # =============================
+        # Creating the desktop file
+        # =============================
+        cat >> $out/share/applications/FG42.desktop << EOF
+        [Desktop Entry]
+        Encoding=UTF-8
+        Name=FG42
+        GenericName=FG42
+        Comment=The nix base Emacs bundle for advance users
+        MimeType=${mimeTypes}
+        Type=Application
+        Terminal=false
+        Categories=Development;TextEditor;
+        StartupWMClass=FG42
+        Exec=${placeholder "out"}/bin/fg42
+        Icon=fg42
+        Version=${version}
+        EOF
+
+        # =============================
+        # Adding the runtime deps to
+        # runtime closure
+        # =============================
+        cat >> $out/share/runtime_deps << EOF
+        ${lib.strings.concatLines runtimeDependencies}
+        ${emacsBundle}
+        EOF
 
 
-  buildPhase = ''
-    runHook preBuild
+        # =============================
+        # Creating fg42 command
+        # =============================
+        cat >> $out/bin/fg42 << EOF
+        #!${stdenv.shell}
 
-    # =============================
-    # Building FG42 itself
-    # =============================
-    LISPDIR=$out/share/fg42/
-    STARTUP_FILE=$LISPDIR/lisp/fg42_init.el
+        export PATH=${pathsStr}:$PATH
+        export FONTCONFIG_FILE="$LISPDIR/fonts.conf"
+        export STARTUP_FILE=$LISPDIR/lisp/fg42_init.el
+        export FG42_PATH=$out
 
-    mkdir -p $out/bin
-    mkdir -p $out/share/applications/
-
-    install -d $LISPDIR
-
-    mkdir -p $LISPDIR/lisp
-    cp -rv ${src}/lisp/build.el $LISPDIR/lisp
-
-    cp -rv ${src}/share $out/
-    cp -rv ${src}/snippets $LISPDIR/snippets
-    cp "${fontsConf}" $LISPDIR/fonts.conf
-    cp "${configFile}" $LISPDIR/config.json
-
-    export FONTCONFIG_FILE="$LISPDIR/fonts.conf"
-    chmod 755 $LISPDIR -R
-
-    emacs --batch -l $LISPDIR/lisp/build.el $LISPDIR/config.json $STARTUP_FILE
-    #emacs -Q --batch -l package --eval "(package-generate-autoloads \"fg42_init" \"$LISPDIR\")"
-    emacs --batch -l loaddefs-gen -f loaddefs-generate-batch $LISPDIR/lisp/ $LISPDIR/lisp/ ${emacsBundle}
-    cd $LISPDIR
-    #compile stuff
-    cd -
-
-    # =============================
-    # Creating the desktop file
-    # =============================
-    cat >> $out/share/applications/FG42.desktop << EOF
-    [Desktop Entry]
-    Encoding=UTF-8
-    Name=FG42
-    GenericName=FG42
-    Comment=The nix base Emacs bundle for advance users
-    MimeType=${mimeTypes}
-    Type=Application
-    Terminal=false
-    Categories=Development;TextEditor;
-    StartupWMClass=FG42
-    Exec=${placeholder "out"}/bin/fg42
-    Icon=fg42
-    Version=${version}
-    EOF
-
-    # =============================
-    # Adding the runtime deps to
-    # runtime closure
-    # =============================
-    cat >> $out/share/runtime_deps << EOF
-    ${lib.strings.concatLines runtimeDependencies}
-    ${emacsBundle}
-    EOF
+        LIBRARY_PATH="\$(${stdenv.cc}/bin/cc -print-file-name=libgccjit.so):\$LIBRARY_PATH" \
+          FG42_WM=fales ${emacsBundle}/bin/emacs \
+          --name FG42 \
+          -q --no-splash --title FG42 \
+          -l "$STARTUP_FILE" "\$@"
+        EOF
+        chmod +x $out/bin/fg42
 
 
-    # =============================
-    # Creating fg42 command
-    # =============================
-    cat >> $out/bin/fg42 << EOF
-    #!${stdenv.shell}
-
-    export PATH=${pathsStr}:$PATH
-    export FONTCONFIG_FILE="$LISPDIR/fonts.conf"
-    export STARTUP_FILE=$LISPDIR/lisp/fg42_init.el
-
-    LIBRARY_PATH="\$(${stdenv.cc}/bin/cc -print-file-name=libgccjit.so):\$LIBRARY_PATH" \
-      FG42_WM=fales ${emacsBundle}/bin/emacs \
-      --name FG42 \
-      -q --no-splash --title FG42 \
-      -l "$STARTUP_FILE" "\$@"
-    EOF
-    chmod +x $out/bin/fg42
+        LISPDIR=$out/share/fg42/lisp/
+        mkdir -p $LISPDIR
+        #emacs --batch -l package --eval "(package-generate-autoloads \"${pname}\" \"$LISPDIR\")"
 
 
-    LISPDIR=$out/share/fg42/lisp/
-    mkdir -p $LISPDIR
-    #emacs --batch -l package --eval "(package-generate-autoloads \"${pname}\" \"$LISPDIR\")"
+        # =============================
+        # Creating the fg42-wm command
+        # =============================
+        cat >> $out/bin/fg42-wm << EOF
+        #!${stdenv.shell}
 
+        export PATH=${pathsStr}:\$PATH
+        export FONTCONFIG_FILE="$LISPDIR/fonts.conf"
+        export STARTUP_FILE=$LISPDIR/lisp/fg42_init.el
+        export FG42_PATH=$out
 
-    # =============================
-    # Creating the fg42-wm command
-    # =============================
-    cat >> $out/bin/fg42-wm << EOF
-    #!${stdenv.shell}
+        # Disable access control for the current user.
+        ${xorg.xhost}/bin/xhost +SI:localuser:\$USER
 
-    export PATH=${pathsStr}:\$PATH
-    export FONTCONFIG_FILE="$LISPDIR/fonts.conf"
-    export STARTUP_FILE=$LISPDIR/lisp/fg42_init.el
+        # Make Java applications aware this is a non-reparenting window manager.
+        export _JAVA_AWT_WM_NONREPARENTING=1
 
-    # Disable access control for the current user.
-    ${xorg.xhost}/bin/xhost +SI:localuser:\$USER
+        # Set default cursor.
+        xsetroot -cursor_name left_ptr
 
-    # Make Java applications aware this is a non-reparenting window manager.
-    export _JAVA_AWT_WM_NONREPARENTING=1
+        # Set keyboard repeat rate.
+        xset r rate 400 30
 
-    # Set default cursor.
-    xsetroot -cursor_name left_ptr
+        # Uncomment the following block to use the exwm-xim module.
+        # export XMODIFIERS=@im=exwm-xim
+        # export GTK_IM_MODULE=xim
+        # export QT_IM_MODULE=xim
+        # export CLUTTER_IM_MODULE=xim
 
-    # Set keyboard repeat rate.
-    xset r rate 400 30
+        LIBRARY_PATH="\$(${stdenv.cc}/bin/cc -print-file-name=libgccjit.so):\$LIBRARY_PATH" \
+          FG42_WM=true ${emacsBundle}/bin/emacs \
+          --name FG42 \
+         -q --no-splash --title FG42 \
+          -l $STARTUP_FILE "\$@"
+        EOF
+        chmod +x $out/bin/fg42-wm
 
-    # Uncomment the following block to use the exwm-xim module.
-    # export XMODIFIERS=@im=exwm-xim
-    # export GTK_IM_MODULE=xim
-    # export QT_IM_MODULE=xim
-    # export CLUTTER_IM_MODULE=xim
+        runHook postBuild
+      '';
 
-    LIBRARY_PATH="\$(${stdenv.cc}/bin/cc -print-file-name=libgccjit.so):\$LIBRARY_PATH" \
-      FG42_WM=true ${emacsBundle}/bin/emacs \
-      --name FG42 \
-     -q --no-splash --title FG42 \
-      -l $STARTUP_FILE "\$@"
-    EOF
-    chmod +x $out/bin/fg42-wm
+      postInstall = ''
+        nixDir=$out/share/fg42/;
+        mkdir -p $nixDir
+        cp -rv flake.nix flake.lock nix/ $nixDir
+      '';
 
-    runHook postBuild
-  '';
+      buildInputs = [ emacs emacsBundle git texinfo gcc bash ];
 
-  buildInputs = [ emacs emacsBundle git texinfo gcc bash ];
+      addEmacsNativeLoadPath = true;
 
-  addEmacsNativeLoadPath = true;
+      meta = {
+        broken = false;
+        platforms = emacs.meta.platforms;
+        homepage = "https://fg42.org/";
+        maintainers = [ maintainers.lxsameer ];
+        description = "The mighty editor for the Emacsians";
+        longDescription = ''
+          FG42 is a framework to create and editor and window manager based on GNU/Emacs.
+          It has a pre-defined setup as well which can be installed out of the box. But the
+          goal of this project is to provide the API necessary to create an integrated editor.
 
-  meta = {
-    broken = false;
-    platforms = emacs.meta.platforms;
-    homepage = "https://fg42.org/";
-    maintainers = [ maintainers.lxsameer ];
-    description = "The mighty editor for the Emacsians";
-    longDescription = ''
-      FG42 is a framework to create and editor and window manager based on GNU/Emacs.
-      It has a pre-defined setup as well which can be installed out of the box. But the
-      goal of this project is to provide the API necessary to create an integrated editor.
+          So you need to know about Emacs in advance.
+        '';
+        license = lib.licenses.gpl3Plus;
+      };
+    };
 
-      So you need to know about Emacs in advance.
-    '';
-    license = lib.licenses.gpl3Plus;
-  };
 }
diff --git a/nix/modules/unit/lisp/fg42.el b/nix/modules/unit/lisp/fg42.el
index 8472545..683cbc4 100644
--- a/nix/modules/unit/lisp/fg42.el
+++ b/nix/modules/unit/lisp/fg42.el
@@ -29,11 +29,18 @@
   (defvar package-archives)
   (defvar use-package-ensure-function))
 
+
 (defun fg42-version ()
   "Return FG42's version."
   (interactive)
   (message "FG42 Version %s" (fg42/config-get "version")))
 
+
+(defun fg42-path ()
+  "Return the path to FG42's installation."
+  (or (getenv "FG42_PATH") (error "'FG42_PATH' is not set!")))
+
+
 (defun defer-garbage-collection ()
   "Disable garbage collection."
   (setq gc-cons-threshold fg42/-gc-cons-threshold))
@@ -84,15 +91,15 @@
   (run-hooks 'fg42/before-user-config-init-hook)
 
   (require 'fg42/themes)
-  
+
   (when (file-exists-p user-init-file)
     (load user-init-file))
-  
+
   (run-hooks 'fg42/after-user-config-init-hook)
-    
+
   (fg42/setup-theme!)
   ;; (fg42/setup-editor)
-  
+
   (add-hook 'emacs-startup-hook
             (lambda ()
               (run-hooks 'fg42/after-init-hook)
diff --git a/nix/modules/unit/lisp/fpkg.el b/nix/modules/unit/lisp/fpkg.el
index 79ee748..a3ef3bf 100644
--- a/nix/modules/unit/lisp/fpkg.el
+++ b/nix/modules/unit/lisp/fpkg.el
@@ -74,5 +74,41 @@ same NAME is set to t."
      (use! ,name ,docs ,@details)))
 
 
+(defun add-to-emacs-load-path (p)
+  "Add the path P to Emacs's load path."
+  (when (file-directory-p p)
+    (add-to-list 'load-path p)))
+
+
+(defun add-emacs-vars (p)
+  "Make the path P available to Emacs."
+  (require 'f)
+  (require 'seq)
+
+  (seq-reduce
+   (lambda (acc x)
+     (when (not (member x acc))
+       (when (f-glob "*.el" x)
+         (cons x acc)
+         (add-to-emacs-load-path x))))
+   (append
+    (f-directories (format "%s/share/emacs/site-lisp" p) nil t)
+    (f-directories (format "%s/share/emacs/native-lisp" p) nil t))
+   nil))
+
+
+(defmacro try! (pkg &rest details)
+  "Try the PKG with the given DETAILS in the running session."
+  (let ((flake-dir (format "%s/share/fg42" (fg42-path)))
+        (cwd (getenv "PWD")))
+    (cd flake-dir)
+    (let* ((output (shell-command-to-string
+                    (format "nix build '.#%s' --no-link --print-out-paths" pkg)))
+           (out (car (string-split output "\n" t))))
+      (add-emacs-vars out)
+      (cd cwd)
+      out)))
+
+
 (provide 'fpkg)
 ;;; fpkg.el ends here