diff --git a/CMakeLists.txt b/CMakeLists.txt
index a879e31f..fc595582 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,6 +36,7 @@ xo_toplevel_compile_options()
 # ----------------------------------------------------------------
 
 #add_subdirectory(src/unit)
+add_subdirectory(example)
 add_subdirectory(utest)
 add_subdirectory(docs)
 
diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
new file mode 100644
index 00000000..ed03faf2
--- /dev/null
+++ b/example/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_subdirectory(ex1)
+add_subdirectory(ex2)
+add_subdirectory(ex3)
diff --git a/example/ex1/CMakeLists.txt b/example/ex1/CMakeLists.txt
new file mode 100644
index 00000000..0d415a06
--- /dev/null
+++ b/example/ex1/CMakeLists.txt
@@ -0,0 +1,14 @@
+# xo-unit/example/ex1/CMakeLists.txt
+
+set(SELF_EXE xo_unit_ex1)
+set(SELF_SRCS ex1.cpp)
+
+add_executable(${SELF_EXE} ${SELF_SRCS})
+xo_include_options2(${SELF_EXE})
+
+# ----------------------------------------------------------------
+# dependencies..
+
+xo_self_dependency(${SELF_EXE} xo_unit)
+
+# end CMakeLists.txt
diff --git a/example/ex1/ex1.cpp b/example/ex1/ex1.cpp
new file mode 100644
index 00000000..74d0dc10
--- /dev/null
+++ b/example/ex1/ex1.cpp
@@ -0,0 +1,18 @@
+/** @file ex1.cpp **/
+
+#include "xo/unit/quantity.hpp"
+#include <iostream>
+
+int
+main () {
+    namespace qty = xo::obs::qty;
+    using namespace std;
+
+    auto t = qty::milliseconds(10);
+    auto m = qty::kilograms(2.5);
+    auto a = m / (t*t);
+
+    cerr << "t: " << t << ", m: " << m << ", m.t^-2: " << a << endl;
+}
+
+/** end ex1.cpp **/
diff --git a/example/ex2/CMakeLists.txt b/example/ex2/CMakeLists.txt
new file mode 100644
index 00000000..fa98d33b
--- /dev/null
+++ b/example/ex2/CMakeLists.txt
@@ -0,0 +1,14 @@
+# xo-unit/example/ex2/CMakeLists.txt
+
+set(SELF_EXE xo_unit_ex2)
+set(SELF_SRCS ex2.cpp)
+
+add_executable(${SELF_EXE} ${SELF_SRCS})
+xo_include_options2(${SELF_EXE})
+
+# ----------------------------------------------------------------
+# dependencies..
+
+xo_self_dependency(${SELF_EXE} xo_unit)
+
+# end CMakeLists.txt
diff --git a/example/ex2/ex2.cpp b/example/ex2/ex2.cpp
new file mode 100644
index 00000000..96e574ed
--- /dev/null
+++ b/example/ex2/ex2.cpp
@@ -0,0 +1,20 @@
+/** @file ex2.cpp **/
+
+#include "xo/unit/quantity.hpp"
+#include <iostream>
+
+int
+main () {
+    namespace u = xo::obs::units;
+    namespace qty = xo::obs::qty;
+    using xo::obs::quantity;
+    using namespace std;
+
+    quantity<u::second> t = qty::milliseconds(10);
+    quantity<u::gram> m = qty::kilograms(2.5);
+    auto a = m / (t*t);
+
+    cerr << "t: " << t << ", m: " << m << ", m.t^-2: " << a << endl;
+}
+
+/** end ex2.cpp **/
diff --git a/example/ex3/CMakeLists.txt b/example/ex3/CMakeLists.txt
new file mode 100644
index 00000000..e6f40fc1
--- /dev/null
+++ b/example/ex3/CMakeLists.txt
@@ -0,0 +1,14 @@
+# xo-unit/example/ex3/CMakeLists.txt
+
+set(SELF_EXE xo_unit_ex3)
+set(SELF_SRCS ex3.cpp)
+
+add_executable(${SELF_EXE} ${SELF_SRCS})
+xo_include_options2(${SELF_EXE})
+
+# ----------------------------------------------------------------
+# dependencies..
+
+xo_self_dependency(${SELF_EXE} xo_unit)
+
+# end CMakeLists.txt
diff --git a/example/ex3/ex3.cpp b/example/ex3/ex3.cpp
new file mode 100644
index 00000000..d7939957
--- /dev/null
+++ b/example/ex3/ex3.cpp
@@ -0,0 +1,19 @@
+/** @file ex3.cpp **/
+
+#include "xo/unit/quantity.hpp"
+#include <iostream>
+
+int
+main () {
+    namespace u = xo::obs::units;
+    namespace qty = xo::obs::qty;
+    using xo::obs::quantity;
+    using namespace std;
+
+    auto t1 = qty::milliseconds(1);
+    auto t2 = qty::minutes(1);
+
+    cerr << "t1: " << t1 << ", t2: " << t2 << ", t1*t2: " << t1*t2 << endl;
+}
+
+/** end ex3.cpp **/