diff --git a/examples/01-blinky/BUILD.gn b/examples/01-blinky/BUILD.gn
index 067afef..0eb2c34 100644
--- a/examples/01-blinky/BUILD.gn
+++ b/examples/01-blinky/BUILD.gn
@@ -39,7 +39,7 @@
     "$dir_pw_log:pw_log",
     "$dir_pw_system:pw_system",
     "$dir_pw_system:work_queue",
-    "//source/pw_board_led:pw_board_led",
+    "//libraries/pw_board_led:pw_board_led",
   ]
 }
 
diff --git a/examples/03-rpc/BUILD.gn b/examples/03-rpc/BUILD.gn
index 8d8c869..50751c9 100644
--- a/examples/03-rpc/BUILD.gn
+++ b/examples/03-rpc/BUILD.gn
@@ -40,8 +40,8 @@
 pw_executable("rpc") {
   sources = [ "main.cc" ]
   deps = [
-    "//source/pw_board_led",
-    "//source/pw_spin_delay",
+    "//libraries/pw_board_led",
+    "//libraries/pw_spin_delay",
     dir_pw_log,
 
     # RPC related dependencies.
diff --git a/examples/04-kvs/BUILD.gn b/examples/04-kvs/BUILD.gn
index 101ff1d..2f70fc3 100644
--- a/examples/04-kvs/BUILD.gn
+++ b/examples/04-kvs/BUILD.gn
@@ -38,8 +38,8 @@
     "$dir_pw_kvs",
     "$dir_pw_kvs:flash_test_partition",
     "$dir_pw_log",
-    "//source/pw_board_led",
-    "//source/pw_spin_delay",
+    "//libraries/pw_board_led",
+    "//libraries/pw_spin_delay",
   ]
 
   # Disable teensy flash tests until the patcher is available.
@@ -48,7 +48,7 @@
   # if (pw_build_EXECUTABLE_TARGET_TYPE == "arduino_executable" &&
   #     pw_arduino_build_CORE_PATH != "" &&
   #     (pw_arduino_build_BOARD == "teensy40" || pw_arduino_build_BOARD == "teensy41")) {
-  #   deps += [ "//source/teensy_flash:teensy_flash_test_partition" ]
+  #   deps += [ "//libraries/teensy_flash:teensy_flash_test_partition" ]
   # } else {
   deps += [ "$dir_pw_kvs:fake_flash_1_aligned_partition" ]
 
diff --git a/examples/05-factory-test/BUILD.gn b/examples/05-factory-test/BUILD.gn
index fe6e070..0fe473e 100644
--- a/examples/05-factory-test/BUILD.gn
+++ b/examples/05-factory-test/BUILD.gn
@@ -42,8 +42,8 @@
 pw_executable("factory_test") {
   sources = [ "main.cc" ]
   deps = [
-    "//source/pw_board_led",
-    "//source/pw_spin_delay",
+    "//libraries/pw_board_led",
+    "//libraries/pw_spin_delay",
     dir_pw_log,
 
     # RPC related dependencies.
diff --git a/source/pw_board_led/BUILD.gn b/libraries/pw_board_led/BUILD.gn
similarity index 100%
rename from source/pw_board_led/BUILD.gn
rename to libraries/pw_board_led/BUILD.gn
diff --git a/source/pw_board_led/public/pw_board_led/led.h b/libraries/pw_board_led/public/pw_board_led/led.h
similarity index 100%
rename from source/pw_board_led/public/pw_board_led/led.h
rename to libraries/pw_board_led/public/pw_board_led/led.h
diff --git a/source/pw_board_led_host/BUILD.gn b/libraries/pw_board_led_host/BUILD.gn
similarity index 93%
rename from source/pw_board_led_host/BUILD.gn
rename to libraries/pw_board_led_host/BUILD.gn
index 1d4b4a3..78eaa25 100644
--- a/source/pw_board_led_host/BUILD.gn
+++ b/libraries/pw_board_led_host/BUILD.gn
@@ -18,7 +18,7 @@
 
 pw_source_set("pw_board_led_host") {
   deps = [
-    "//source/pw_board_led:pw_board_led.facade",
+    "//libraries/pw_board_led:pw_board_led.facade",
     dir_pw_log,
   ]
   sources = [ "led.cc" ]
diff --git a/source/pw_board_led_host/led.cc b/libraries/pw_board_led_host/led.cc
similarity index 100%
rename from source/pw_board_led_host/led.cc
rename to libraries/pw_board_led_host/led.cc
diff --git a/source/pw_board_led_stm32f429i_disc1/BUILD.gn b/libraries/pw_board_led_stm32f429i_disc1/BUILD.gn
similarity index 93%
rename from source/pw_board_led_stm32f429i_disc1/BUILD.gn
rename to libraries/pw_board_led_stm32f429i_disc1/BUILD.gn
index 29cb634..98e32ec 100644
--- a/source/pw_board_led_stm32f429i_disc1/BUILD.gn
+++ b/libraries/pw_board_led_stm32f429i_disc1/BUILD.gn
@@ -18,7 +18,7 @@
 
 pw_source_set("pw_board_led_stm32f429i_disc1") {
   deps = [
-    "//source/pw_board_led:pw_board_led.facade",
+    "//libraries/pw_board_led:pw_board_led.facade",
     dir_pw_preprocessor,
   ]
   sources = [ "led.cc" ]
diff --git a/source/pw_board_led_stm32f429i_disc1/led.cc b/libraries/pw_board_led_stm32f429i_disc1/led.cc
similarity index 100%
rename from source/pw_board_led_stm32f429i_disc1/led.cc
rename to libraries/pw_board_led_stm32f429i_disc1/led.cc
diff --git a/source/pw_board_led_teensy/BUILD.gn b/libraries/pw_board_led_teensy/BUILD.gn
similarity index 94%
rename from source/pw_board_led_teensy/BUILD.gn
rename to libraries/pw_board_led_teensy/BUILD.gn
index 8a5f9d7..b1b5e47 100644
--- a/source/pw_board_led_teensy/BUILD.gn
+++ b/libraries/pw_board_led_teensy/BUILD.gn
@@ -20,7 +20,7 @@
 pw_source_set("pw_board_led_teensy") {
   deps = [
     "$dir_pw_third_party/arduino:arduino_core_sources",
-    "//source/pw_board_led:pw_board_led.facade",
+    "//libraries/pw_board_led:pw_board_led.facade",
   ]
   sources = [ "led.cc" ]
   remove_configs = [ "$dir_pw_build:strict_warnings" ]
diff --git a/source/pw_board_led_teensy/led.cc b/libraries/pw_board_led_teensy/led.cc
similarity index 100%
rename from source/pw_board_led_teensy/led.cc
rename to libraries/pw_board_led_teensy/led.cc
diff --git a/source/pw_spin_delay/BUILD.gn b/libraries/pw_spin_delay/BUILD.gn
similarity index 100%
rename from source/pw_spin_delay/BUILD.gn
rename to libraries/pw_spin_delay/BUILD.gn
diff --git a/source/pw_spin_delay/public/pw_spin_delay/delay.h b/libraries/pw_spin_delay/public/pw_spin_delay/delay.h
similarity index 100%
rename from source/pw_spin_delay/public/pw_spin_delay/delay.h
rename to libraries/pw_spin_delay/public/pw_spin_delay/delay.h
diff --git a/source/pw_spin_delay_arduino/BUILD.gn b/libraries/pw_spin_delay_arduino/BUILD.gn
similarity index 94%
rename from source/pw_spin_delay_arduino/BUILD.gn
rename to libraries/pw_spin_delay_arduino/BUILD.gn
index 72937ae..c673da2 100644
--- a/source/pw_spin_delay_arduino/BUILD.gn
+++ b/libraries/pw_spin_delay_arduino/BUILD.gn
@@ -20,7 +20,7 @@
 pw_source_set("pw_spin_delay_arduino") {
   deps = [
     "$dir_pw_third_party/arduino:arduino_core_sources",
-    "//source/pw_spin_delay:pw_spin_delay.facade",
+    "//libraries/pw_spin_delay:pw_spin_delay.facade",
   ]
   sources = [ "delay.cc" ]
   remove_configs = [ "$dir_pw_build:strict_warnings" ]
diff --git a/source/pw_spin_delay_arduino/delay.cc b/libraries/pw_spin_delay_arduino/delay.cc
similarity index 100%
rename from source/pw_spin_delay_arduino/delay.cc
rename to libraries/pw_spin_delay_arduino/delay.cc
diff --git a/source/pw_spin_delay_host/BUILD.gn b/libraries/pw_spin_delay_host/BUILD.gn
similarity index 91%
rename from source/pw_spin_delay_host/BUILD.gn
rename to libraries/pw_spin_delay_host/BUILD.gn
index 65c5571..5af12b0 100644
--- a/source/pw_spin_delay_host/BUILD.gn
+++ b/libraries/pw_spin_delay_host/BUILD.gn
@@ -17,6 +17,6 @@
 import("$dir_pw_build/target_types.gni")
 
 pw_source_set("pw_spin_delay_host") {
-  deps = [ "//source/pw_spin_delay:pw_spin_delay.facade" ]
+  deps = [ "//libraries/pw_spin_delay:pw_spin_delay.facade" ]
   sources = [ "delay.cc" ]
 }
diff --git a/source/pw_spin_delay_host/delay.cc b/libraries/pw_spin_delay_host/delay.cc
similarity index 100%
rename from source/pw_spin_delay_host/delay.cc
rename to libraries/pw_spin_delay_host/delay.cc
diff --git a/source/pw_spin_delay_stm32f429i_disc1/BUILD.gn b/libraries/pw_spin_delay_stm32f429i_disc1/BUILD.gn
similarity index 93%
rename from source/pw_spin_delay_stm32f429i_disc1/BUILD.gn
rename to libraries/pw_spin_delay_stm32f429i_disc1/BUILD.gn
index 991bdac..72bdaad 100644
--- a/source/pw_spin_delay_stm32f429i_disc1/BUILD.gn
+++ b/libraries/pw_spin_delay_stm32f429i_disc1/BUILD.gn
@@ -18,7 +18,7 @@
 
 pw_source_set("pw_spin_delay_stm32f429i_disc1") {
   deps = [
-    "//source/pw_spin_delay:pw_spin_delay.facade",
+    "//libraries/pw_spin_delay:pw_spin_delay.facade",
     dir_pw_preprocessor,
   ]
   sources = [ "delay.cc" ]
diff --git a/source/pw_spin_delay_stm32f429i_disc1/delay.cc b/libraries/pw_spin_delay_stm32f429i_disc1/delay.cc
similarity index 100%
rename from source/pw_spin_delay_stm32f429i_disc1/delay.cc
rename to libraries/pw_spin_delay_stm32f429i_disc1/delay.cc
diff --git a/targets/arduino/target_toolchains.gni b/targets/arduino/target_toolchains.gni
index 7368c16..094a734 100644
--- a/targets/arduino/target_toolchains.gni
+++ b/targets/arduino/target_toolchains.gni
@@ -48,8 +48,8 @@
     defaults = {
       forward_variables_from(_toolchain_base.defaults, "*")
       forward_variables_from(toolchain_overrides, "*")
-      pw_board_led_BACKEND = "//source/pw_board_led_teensy"
-      pw_spin_delay_BACKEND = "//source/pw_spin_delay_arduino"
+      pw_board_led_BACKEND = "//libraries/pw_board_led_teensy"
+      pw_spin_delay_BACKEND = "//libraries/pw_spin_delay_arduino"
     }
   }
 
diff --git a/targets/host/BUILD.gn b/targets/host/BUILD.gn
index 2eff273..93275d6 100644
--- a/targets/host/BUILD.gn
+++ b/targets/host/BUILD.gn
@@ -23,7 +23,7 @@
   scheduler = PW_SYSTEM_SCHEDULER.NATIVE
   link_deps = [ "$dir_pigweed/targets/host_device_simulator:boot" ]
   build_args = {
-    pw_board_led_BACKEND = "//source/pw_board_led_host"
+    pw_board_led_BACKEND = "//libraries/pw_board_led_host"
   }
 }
 
diff --git a/targets/host/target_toolchains.gni b/targets/host/target_toolchains.gni
index 112f249..18c9ff3 100644
--- a/targets/host/target_toolchains.gni
+++ b/targets/host/target_toolchains.gni
@@ -64,8 +64,8 @@
 
       # Configure backend for pw_sys_io facade.
       pw_sys_io_BACKEND = dir_pw_sys_io_stdio
-      pw_board_led_BACKEND = "//source/pw_board_led_host"
-      pw_spin_delay_BACKEND = "//source/pw_spin_delay_host"
+      pw_board_led_BACKEND = "//libraries/pw_board_led_host"
+      pw_spin_delay_BACKEND = "//libraries/pw_spin_delay_host"
     }
   }
 
diff --git a/targets/stm32f429i_disc1/BUILD.gn b/targets/stm32f429i_disc1/BUILD.gn
index ef185f9..74f3f3a 100644
--- a/targets/stm32f429i_disc1/BUILD.gn
+++ b/targets/stm32f429i_disc1/BUILD.gn
@@ -35,7 +35,7 @@
     pw_third_party_stm32cube_CONFIG =
         "$dir_pigweed/targets/stm32f429i_disc1_stm32cube:stm32f4xx_hal_config"
     pw_third_party_stm32cube_CORE_INIT = ""
-    pw_board_led_BACKEND = "//source/pw_board_led_stm32f429i_disc1"
+    pw_board_led_BACKEND = "//libraries/pw_board_led_stm32f429i_disc1"
     pw_boot_cortex_m_LINK_CONFIG_DEFINES = [
       "PW_BOOT_FLASH_BEGIN=0x08000200",
       "PW_BOOT_FLASH_SIZE=2048K",
diff --git a/targets/stm32f429i_disc1/target_toolchains.gni b/targets/stm32f429i_disc1/target_toolchains.gni
index 4c9f68d..56e2e9d 100644
--- a/targets/stm32f429i_disc1/target_toolchains.gni
+++ b/targets/stm32f429i_disc1/target_toolchains.gni
@@ -34,8 +34,8 @@
     "$dir_pw_log:impl",
   ]
 
-  pw_board_led_BACKEND = "//source/pw_board_led_stm32f429i_disc1"
-  pw_spin_delay_BACKEND = "//source/pw_spin_delay_stm32f429i_disc1"
+  pw_board_led_BACKEND = "//libraries/pw_board_led_stm32f429i_disc1"
+  pw_spin_delay_BACKEND = "//libraries/pw_spin_delay_stm32f429i_disc1"
 }
 
 target_toolchain_stm32f429i_disc1 = {