diff --git a/notebooks/index.clj b/notebooks/index.clj
index d536a849..03993c8e 100644
--- a/notebooks/index.clj
+++ b/notebooks/index.clj
@@ -90,6 +90,7 @@
   [:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/x_add_side_dependency_test.clj")} "Add a side dependency"]]
   #_[:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/x_instrument_test.clj")} "Instrument"]]
   [:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/x_update_key_test.clj")} "Update key"]]
+  [:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/x_log_test.clj")} "Log"]]
   [:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/y_graceful_stop_test.clj")} "Graceful stop"]]
   [:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/y_multi_arity_service_test.clj")} "Multi arity service"]]
   [:li [:a {:href (clerk/doc-url "test/darkleaf/di/tutorial/z_multi_system_test.clj")} "Multi system"]]
diff --git a/src/darkleaf/di/core.clj b/src/darkleaf/di/core.clj
index 00159dc9..b96998f9 100644
--- a/src/darkleaf/di/core.clj
+++ b/src/darkleaf/di/core.clj
@@ -797,3 +797,27 @@
                ~@body))
            (finally
              (.close resource#)))))))
+
+(defn log
+  "A logging middleware.
+  Calls `:after-build!` and `:after-demolish!` during `di/start`.
+  Must be the last one in the middleware chain.
+  Both callbacks are expected to accept
+  the following arg `{:keys [key object]}`."
+  [& {:keys [after-build! after-demolish!]
+      :or   {after-build!    (fn no-op [_])
+             after-demolish! (fn no-op [_])}}]
+  (fn [registry]
+    (fn [key]
+      (let [factory (registry key)]
+        (reify p/Factory
+          (dependencies [_]
+            (p/dependencies factory))
+          (build [_ deps]
+            (let [obj (p/build factory deps)]
+              (after-build! {:key key :object obj})
+              obj))
+          (demolish [_ obj]
+            (p/demolish factory obj)
+            (after-demolish! {:key key :object obj})
+            nil))))))
diff --git a/test/darkleaf/di/add_side_dependency_test.clj b/test/darkleaf/di/add_side_dependency_test.clj
index 408892d0..dbfeded6 100644
--- a/test/darkleaf/di/add_side_dependency_test.clj
+++ b/test/darkleaf/di/add_side_dependency_test.clj
@@ -26,62 +26,55 @@
 
 (defn- a
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :a)
+  []
   :a)
 
 (defn- b
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :b)
+  []
   :b)
 
 (defn- c
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :c)
+  []
   :c)
 
 (defn- d
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :d)
+  []
   :d)
 
 (defn- e
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :e)
+  []
   :e)
 
 (defn- f
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :f)
+  []
   :f)
 
 (defn- g
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :g)
+  []
   :g)
 
 (defn- h
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :h)
+  []
   :h)
 
 (defn- side-dep
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :side-dep))
+  []
+  :side-dep)
 
 (t/deftest bug-array-map->hash-map
-  (let [log (atom [])]
+  (let [log          (atom [])
+        after-build! (fn [{:keys [key]}]
+                       (swap! log conj key))]
     (with-open [root (di/start ::root
-                               {::log  log
-                                ::root (di/template
+                               {::root (di/template
                                         {:a (di/ref `a)
                                          :b (di/ref `b)
                                          :c (di/ref `c)
@@ -90,8 +83,9 @@
                                          :f (di/ref `f)
                                          :g (di/ref `g)
                                          :h (di/ref `h)})}
-                               (di/add-side-dependency `side-dep))]
-      (t/is (= [:a :b :c :d :e :f :g :h :side-dep] @log))
+                               (di/add-side-dependency `side-dep)
+                               (di/log :after-build! after-build!))]
+      (t/is (= [`a `b `c `d `e `f `g `h `di/new-key#0 `side-dep ::root] @log))
       (t/is (= {:a :a
                 :b :b
                 :c :c
@@ -103,13 +97,14 @@
 
 (defn- side-dep2
   {::di/kind :component}
-  [{log ::log}]
-  (swap! log conj :side-dep2))
+  []
+  :side-dep2)
 
 (t/deftest bug-array-map->hash-map-2
-  (let [log (atom [])]
+  (let [log          (atom [])
+        after-build! (fn [{:keys [key]}]
+                       (swap! log conj key))]
     (with-open [root (di/start ::root
-                               {::log  log}
                                (di/add-side-dependency `side-dep)
                                {::root (di/template
                                         {:a (di/ref `a)
@@ -120,8 +115,11 @@
                                          :f (di/ref `f)
                                          :g (di/ref `g)
                                          :h (di/ref `h)})}
-                               (di/add-side-dependency `side-dep2))]
-      (t/is (= [:a :side-dep :b :c :d :e :f :g :h :side-dep2] @log))
+                               (di/add-side-dependency `side-dep2)
+                               (di/log :after-build! after-build!))]
+      (t/is (= [`di/new-key#0 `side-dep `a
+                `b `c `d `e `f `g `h
+                `di/new-key#1 `side-dep2 ::root] @log))
       (t/is (= {:a :a
                 :b :b
                 :c :c
diff --git a/test/darkleaf/di/dependencies_test.clj b/test/darkleaf/di/dependencies_test.clj
index 14cded89..0c87e1bf 100644
--- a/test/darkleaf/di/dependencies_test.clj
+++ b/test/darkleaf/di/dependencies_test.clj
@@ -11,33 +11,33 @@
 ;;   c
 
 (defn root
-  {::di/stop #(swap! % conj [`root :stopped])}
-  [{a `a, b `b, log ::log}]
-  (swap! log conj [`root :built])
-  log)
+  {::di/kind :component}
+  [{a `a, b `b}]
+  :root)
 
 (defn a
-  {::di/stop #(swap! % conj [`a :stopped])}
-  [{c `c, log ::log}]
-  (swap! log conj [`a :built])
-  log)
+  {::di/kind :component}
+  [{c `c}]
+  :a)
 
 (defn b
-  {::di/stop #(swap! % conj [`b :stopped])}
-  [{c `c, log ::log}]
-  (swap! log conj [`b :built])
-  log)
+  {::di/kind :component}
+  [{c `c}]
+  :b)
 
 (defn c
-  {::di/stop #(swap! % conj [`c :stopped])}
-  [{log ::log}]
-  (swap! log conj [`c :built])
-  log)
+  {::di/kind :component}
+  []
+  :c)
 
 (t/deftest order-test
-  (let [log (atom [])]
-    (-> (di/start `root {::log log})
-        (di/stop))
+  (let [log             (atom [])
+        after-build!    (fn [{:keys [key]}]
+                          (swap! log conj [key :built]))
+        after-demolish! (fn [{:keys [key]}]
+                          (swap! log conj [key :stopped]))]
+    (with-open [root (di/start `root (di/log :after-build!    after-build!
+                                             :after-demolish! after-demolish!))])
     (t/is (= [[`c :built]
               [`a :built]
               [`b :built]
diff --git a/test/darkleaf/di/tutorial/x_log_test.clj b/test/darkleaf/di/tutorial/x_log_test.clj
new file mode 100644
index 00000000..ae8fa1ae
--- /dev/null
+++ b/test/darkleaf/di/tutorial/x_log_test.clj
@@ -0,0 +1,35 @@
+(ns darkleaf.di.tutorial.x-log-test
+  (:require
+   [clojure.test :as t]
+   [darkleaf.di.core :as di]))
+
+(defn a
+  {::di/kind :component}
+  []
+  :a)
+
+(defn b [{a `a}]
+  :b)
+
+(defn c
+  {::di/kind :component}
+  [{b `b}]
+  :c)
+
+(t/deftest log
+  (let [logs            (atom [])
+        after-build!    (fn [{:keys [key object]}]
+                          (swap! logs conj [:built      key (pr-str object)]))
+        after-demolish! (fn [{:keys [key object]}]
+                          (swap! logs conj [:demolished key (pr-str object)]))]
+    (with-open [root (di/start `c (di/log :after-build!    after-build!
+                                          :after-demolish! after-demolish!))])
+    (t/is (= [[:built `a ":a"]
+              [:built `b
+               "#darkleaf.di.core/service #'darkleaf.di.tutorial.x-log-test/b"]
+              [:built `c ":c"]
+              [:demolished `c ":c"]
+              [:demolished `b
+               "#darkleaf.di.core/service #'darkleaf.di.tutorial.x-log-test/b"]
+              [:demolished `a ":a"]]
+             @logs))))