diff --git a/garlic/exp/nbody/tampi.nix b/garlic/exp/nbody/tampi.nix
index ca2745d..c5fd69f 100644
--- a/garlic/exp/nbody/tampi.nix
+++ b/garlic/exp/nbody/tampi.nix
@@ -17,7 +17,7 @@ let
     cc = [ bsc.icc ];
     mpi = [ bsc.impi ];
     #mpi = [ bsc.mpichDebug ];
-    blocksize = [ 1024 ];
+    blocksize = [ 1024 2048 ];
   };
 
   # Common configuration
@@ -164,7 +164,7 @@ let
       inherit cc blocksize mpi gitBranch;
     };
 
-  launch = w.launch.override {
+  experimentFn = w.experiment.override {
     nixPrefix = common.nixPrefix;
   };
 
@@ -193,13 +193,14 @@ let
   stages = stdStages ++ debugStages ++ [ argv nbodyFn ];
 
   # List of actual programs to be executed
-  jobs = map (conf: w.stagen { inherit conf stages; }) configs;
+  units = map (conf: w.unit { inherit conf stages; }) configs;
 
-  launcher = launch jobs;
+  experiment = experimentFn units;
 
   trebuchet = stage: w.trebuchet {
     program = stageProgram stage;
     nixPrefix = common.nixPrefix;
+    experiment = experiment;
   };
 
   isolatedRun = stage: isolate {
@@ -207,9 +208,10 @@ let
     conf = common;
   };
 
-  final = trebuchet (isolatedRun launcher);
+  final = trebuchet (isolatedRun experiment);
 
 in
   # We simply run each program one after another
   #launch jobs
   final
+  #jobs
diff --git a/garlic/stages/experiment/default.nix b/garlic/stages/experiment/default.nix
new file mode 100644
index 0000000..a397fbc
--- /dev/null
+++ b/garlic/stages/experiment/default.nix
@@ -0,0 +1,34 @@
+{
+  stdenv
+, nixPrefix ? ""
+}:
+
+units:
+
+with stdenv.lib;
+
+let
+  stageProgram = stage:
+    if stage ? programPath
+    then "${stage}${stage.programPath}" else "${stage}";
+
+  unitsString = builtins.concatStringsSep "\n"
+    (map (x: "${stageProgram x}") units);
+in
+stdenv.mkDerivation {
+  name = "experiment";
+  phases = [ "installPhase" ];
+  preferLocalBuild = true;
+  dontPatchShebangs = true;
+  inherit units;
+
+  installPhase = ''
+    cat > $out << EOF
+    #!/bin/sh
+
+    # This is an experiment formed by the following units:
+    ${unitsString}
+    EOF
+    chmod +x $out
+  '';
+}
diff --git a/garlic/stages/experiment/old.nix b/garlic/stages/experiment/old.nix
new file mode 100644
index 0000000..763bdb4
--- /dev/null
+++ b/garlic/stages/experiment/old.nix
@@ -0,0 +1,50 @@
+{
+  stdenv
+, nixPrefix ? ""
+}:
+
+apps: # Each app must be unique
+
+stdenv.mkDerivation {
+  name = "launcher";
+  preferLocalBuild = true;
+
+  buildInputs = [] ++ apps;
+  apps = apps;
+  phases = [ "unpackPhase" "patchPhase" "installPhase" ];
+  dontPatchShebangs = true;
+  programPath = "/bin/run";
+
+  src = ./.;
+
+  inherit nixPrefix;
+
+  patchPhase = ''
+    substituteAllInPlace run
+  '';
+
+  installPhase = ''
+    mkdir -p $out/apps
+    for j in $apps; do
+      target=$out/apps/$(basename $j)
+      if [ -e $target ]; then
+        echo "Duplicated app: $j"
+        echo
+        echo "Provided apps: "
+        printf "%s\n" $apps
+        echo
+        exit 1
+      fi
+      ln -s $j $target
+    done
+
+    mkdir -p $out/bin
+    install -m755 run $out/bin/run
+    chmod +x $out/bin/*
+
+    # Mark the launcher for upload
+    touch $out/.upload-to-mn
+    # And mark it as an experiment
+    touch $out/.experiment
+  '';
+}
diff --git a/garlic/stages/experiment/run b/garlic/stages/experiment/run
new file mode 100644
index 0000000..3c98c2c
--- /dev/null
+++ b/garlic/stages/experiment/run
@@ -0,0 +1,20 @@
+#!/bin/sh -ex
+
+>&2 echo "Running launcher"
+
+if [ ! -e "/nix" ]; then
+  >&2 echo "missing /nix"
+  exit 1
+fi
+
+if [ -z "$GARLIC_OUT" ]; then
+  >&2 echo "GARLIC_OUT is not set"
+  exit 1
+fi
+
+mkdir -p "$GARLIC_OUT"
+cd "$GARLIC_OUT"
+
+for j in @out@/apps/*; do
+  $j/bin/run
+done
diff --git a/garlic/stages/launcher/default.nix b/garlic/stages/launcher/default.nix
index 763bdb4..aa019da 100644
--- a/garlic/stages/launcher/default.nix
+++ b/garlic/stages/launcher/default.nix
@@ -3,48 +3,33 @@
 , nixPrefix ? ""
 }:
 
-apps: # Each app must be unique
+units:
 
+with stdenv.lib;
+
+let
+
+  stageProgram = stage:
+    if stage ? programPath
+    then "${stage}${stage.programPath}" else "${stage}";
+
+  unitsString = builtins.concatStringsSep "\n"
+    (map (x: "${stageProgram x}") units);
+in
 stdenv.mkDerivation {
-  name = "launcher";
+  name = "experiment";
+  phases = [ "installPhase" ];
   preferLocalBuild = true;
-
-  buildInputs = [] ++ apps;
-  apps = apps;
-  phases = [ "unpackPhase" "patchPhase" "installPhase" ];
   dontPatchShebangs = true;
-  programPath = "/bin/run";
-
-  src = ./.;
-
-  inherit nixPrefix;
-
-  patchPhase = ''
-    substituteAllInPlace run
-  '';
+  inherit units;
 
   installPhase = ''
-    mkdir -p $out/apps
-    for j in $apps; do
-      target=$out/apps/$(basename $j)
-      if [ -e $target ]; then
-        echo "Duplicated app: $j"
-        echo
-        echo "Provided apps: "
-        printf "%s\n" $apps
-        echo
-        exit 1
-      fi
-      ln -s $j $target
-    done
+    cat > $out << EOF
+    #!/bin/sh
 
-    mkdir -p $out/bin
-    install -m755 run $out/bin/run
-    chmod +x $out/bin/*
-
-    # Mark the launcher for upload
-    touch $out/.upload-to-mn
-    # And mark it as an experiment
-    touch $out/.experiment
+    # This is an experiment formed by the following units:
+    ${unitsString}
+    EOF
+    chmod +x $out
   '';
 }
diff --git a/garlic/stages/launcher/old.nix b/garlic/stages/launcher/old.nix
new file mode 100644
index 0000000..763bdb4
--- /dev/null
+++ b/garlic/stages/launcher/old.nix
@@ -0,0 +1,50 @@
+{
+  stdenv
+, nixPrefix ? ""
+}:
+
+apps: # Each app must be unique
+
+stdenv.mkDerivation {
+  name = "launcher";
+  preferLocalBuild = true;
+
+  buildInputs = [] ++ apps;
+  apps = apps;
+  phases = [ "unpackPhase" "patchPhase" "installPhase" ];
+  dontPatchShebangs = true;
+  programPath = "/bin/run";
+
+  src = ./.;
+
+  inherit nixPrefix;
+
+  patchPhase = ''
+    substituteAllInPlace run
+  '';
+
+  installPhase = ''
+    mkdir -p $out/apps
+    for j in $apps; do
+      target=$out/apps/$(basename $j)
+      if [ -e $target ]; then
+        echo "Duplicated app: $j"
+        echo
+        echo "Provided apps: "
+        printf "%s\n" $apps
+        echo
+        exit 1
+      fi
+      ln -s $j $target
+    done
+
+    mkdir -p $out/bin
+    install -m755 run $out/bin/run
+    chmod +x $out/bin/*
+
+    # Mark the launcher for upload
+    touch $out/.upload-to-mn
+    # And mark it as an experiment
+    touch $out/.experiment
+  '';
+}
diff --git a/garlic/stages/trebuchet/default.nix b/garlic/stages/trebuchet/default.nix
index 68405f4..6b397c7 100644
--- a/garlic/stages/trebuchet/default.nix
+++ b/garlic/stages/trebuchet/default.nix
@@ -8,8 +8,37 @@
 , nixPrefix
 , sshHost ? "mn"
 , targetCluster ? "mn4"
+, experiment ? ""
 }:
 
+with stdenv.lib;
+
+let
+
+  dStages = foldr (stageFn: {conf, prevStage, stages}: {
+    conf = conf;
+    prevStage = stageFn {stage=prevStage; conf=conf;};
+    stages = [ (stageFn {stage=prevStage; conf=conf;}) ] ++ stages;
+  })
+    {conf=conf; stages=[]; prevStage=null;} stages;
+
+  stageProgram = stage:
+    if stage ? programPath
+    then "${stage}${stage.programPath}" else "${stage}";
+
+  linkStages = imap1 (i: s: {
+    num = "${toString i}";
+    name = "${toString i}-${baseNameOf s.name}";
+    stage = s;
+    programPath = stageProgram s;
+  }) dStages.stages;
+
+  units = builtins.concatStringsSep "\n"
+    (map (x: "#  ${x}") experiment.units);
+
+  firstStage = (x: x.programPath) (elemAt linkStages 0);
+in
+
 stdenv.mkDerivation {
   name = "trebuchet";
   phases = [ "installPhase" ];
@@ -23,6 +52,12 @@ stdenv.mkDerivation {
     # Take a look at ${program}
     # to see what is being executed.
 
+    # Executes the following experiment in MN4:
+    #  ${experiment}
+
+    # Which contains the following experiment units:
+    ${units}
+
     nixtools=${nixPrefix}${nixtools}/bin
     runexp=\$nixtools/${targetCluster}/runexp
 
diff --git a/garlic/stages/unit.nix b/garlic/stages/unit.nix
new file mode 100644
index 0000000..f20a4dd
--- /dev/null
+++ b/garlic/stages/unit.nix
@@ -0,0 +1,62 @@
+{
+  stdenv
+, bash
+}:
+
+{
+  stages
+, conf
+}:
+
+with stdenv.lib;
+
+let
+
+  dStages = foldr (stageFn: {conf, prevStage, stages}: {
+    conf = conf;
+    prevStage = stageFn {stage=prevStage; conf=conf;};
+    stages = [ (stageFn {stage=prevStage; conf=conf;}) ] ++ stages;
+  })
+    {conf=conf; stages=[]; prevStage=null;} stages;
+
+  stageProgram = stage:
+    if stage ? programPath
+    then "${stage}${stage.programPath}" else "${stage}";
+
+  linkStages = imap1 (i: s: {
+    num = "${toString i}";
+    name = "${toString i}-${baseNameOf s.name}";
+    stage = s;
+    programPath = stageProgram s;
+  }) dStages.stages;
+
+  stageList = builtins.concatStringsSep "\n"
+    (map (x: "#  ${x.stage}") linkStages);
+
+  firstStage = (x: x.programPath) (elemAt linkStages 0);
+in
+stdenv.mkDerivation {
+  name = "unit";
+  preferLocalBuild = true;
+  phases = [ "installPhase" ];
+  installPhase = ''
+    cat > $out << EOF
+    #!/bin/sh -e
+
+    # This script defines an experimental unit with the following stages:
+    ${stageList}
+
+    # Set the experiment unit in the environment
+    export GARLIC_UNIT=$(basename $out)
+
+    # And change the working directory
+    mkdir \$GARLIC_UNIT
+    cd \$GARLIC_UNIT
+
+    # Finally, execute the first stage:
+    exec ${firstStage}
+    EOF
+
+    chmod +x $out
+  '';
+}
diff --git a/overlay.nix b/overlay.nix
index 8b848fd..72de9e2 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -209,6 +209,8 @@ let
         isolate   = callPackage ./garlic/stages/isolate { };
         trebuchet = callPackage ./garlic/stages/trebuchet { };
         strace    = callPackage ./garlic/stages/strace.nix { };
+        unit      = callPackage ./garlic/stages/unit.nix { };
+        experiment= callPackage ./garlic/stages/experiment/default.nix { };
       };
 
       # Tests (move to bsc ?)