diff --git a/.env.example b/.env.example
index 98cfe7b..61f5795 100644
--- a/.env.example
+++ b/.env.example
@@ -6,11 +6,11 @@
 # - configure the Docker external port mapping for the postgres container
 #
 # Procedure:
-# - Set a value for POSTGRES_PASSWORD, and LEARNDEV_DB_PASSWORD.
+# - Set a value for POSTGRES_PASSWORD, LEARNDEV_DB_PASSWORD, MONGO_ROOT_PASSWORD
 # - Leave other variables unchanged because defaults are fine.
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-# ~~~ Postgres Docker container port mapping ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# ~~~ External port mapping for the postgres Docker container  ~~~~~~~~~~~~~~~~~~~~~
 
 # Host port mapped to the internal Postgres container's port 5432.
 # Only the host side is configurable here. 5432 is fixed inside the container.
@@ -22,7 +22,7 @@ POSTGRES_PORT=5433
 # Exposed postgres host network interface.
 # Docker accepts incoming requests on this interface and routes them
 #   to Postgres running in the Docker container.
-# Default value is 0.0.0.0 (IP v4)) and :: (IP V6),
+# Default value (if unset) is 0.0.0.0 (IP v4) and :: (IP V6),
 #   meaning all network interfaces.
 # See: https://docs.docker.com/engine/reference/commandline/run/#publish
 #
@@ -55,13 +55,13 @@ POSTGRES_HOST_AUTH_METHOD=scram-sha-256
 POSTGRES_PASSWORD=TODO_SET_A_VALUE_HERE
 
 
-# ~~~ Application database and user  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# ~~~ Postgres application database and user  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 # Created by docker/init/01-create-app-db-user.sh **on first** container start.
 # These variables are also referenced in Spring Boot's application.yaml
 # configuration file to configure the datasource.
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-# Name of the application database.
+# Name of the (Postgres) application database,
 #
 LEARNDEV_DB_NAME=learndev
 
@@ -75,6 +75,39 @@ LEARNDEV_DB_USER=learndev
 LEARNDEV_DB_PASSWORD=TODO_SET_A_VALUE_HERE
 
 
+# ~~~~ MongoDB  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+# Name of the MongoDB admin user
+#
+MONGO_ROOT_USERNAME=mongoadmin
+
+# Password for the MongoDB admin user
+#
+MONGO_ROOT_PASSWORD=TODO_SET_A_VALUE_HERE
+
+# Name of the MongoDB application database
+#
+LEARNDEV_MONGO_DB_NAME=learndev
+
+
+# ~~~ External port mapping for the mongo Docker Compose service ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+# Exposed MongoDB host network interface.
+# Docker accepts incoming requests on this interface and routes them
+#   to MongoDB running in the Docker container.
+# Default value (**if unset**) is 0.0.0.0 (IP v4) and :: (IP V6),
+#   meaning all network interfaces.
+# See: https://docs.docker.com/engine/reference/commandline/run/#publish
+#
+MONGO_HOST=127.0.0.1
+
+# MongoDB port mapped to the internal mongo container's port 27017.
+# Only the host side is configurable here. 27017 is fixed inside the container.
+# Use a non-standard port (e.g. 27018) to avoid clashing with a local MongoDB install.
+#
+MONGO_PORT=27018
+
+
 # ~~~~ Spring Boot  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 # Default Spring Boot active profile: dev
diff --git a/README.md b/README.md
index beccd4b..070824a 100644
--- a/README.md
+++ b/README.md
@@ -69,27 +69,158 @@ See the [Tech Stack](#tech-stack) section.
 
 ### Installation
 
-TODO
+- Clone the `ebouchut/learn-dev` Git Repository
+- Install Docker, Docker Desktop, and Docker Compose
+
+#### Clone the Git repository
+
+```shell
+#
+git clone git@github.com:ebouchut/learn-dev.git
+# git clone https://github.com/ebouchut/learn-dev.git
+
+cd learn-dev
+```
 
 #### Docker Setup
 
 From the project root folder.
+Install _Docker_ and _Docker Compose_:
+
+- on macOS (read [this for Windows or Linux install](https://docs.docker.com/get-started/get-docker/)):  
+  ```shell
+  brew install docker docker-compose docker-desktop
+  ```
+- on [Windows and Linux](https://docs.docker.com/get-started/get-docker/)
+
+
+## Configuration
+
+- Edit `.env`
+  - [ ] Set a value for the variables `POSTGRES_PASSWORD`, `LEARNDEV_DB_PASSWORD`, `MONGO_ROOT_PASSWORD`
+
+
+## Run the application
+
+This starts all the Docker services for the application:
 
-- Install Docker 
-  - on macOS (read [this for Windows or Linux install](https://docs.docker.com/get-started/get-docker/)):  
-    ```shell
-    brew install docker docker-compose docker-desktop
-    ```
-  - on [Windows and Linux](https://docs.docker.com/get-started/get-docker/)
-- Downloads the Docker images for this application,
-  then runs the containers configured in the  `docker-compose.yaml` configuration file:
   ```shell
   docker compose up -d
-  docker compose logs
   ```
-  A Docker init script creates the application database and user when the `learn-dev-postgres` container 
-  is run for the first time.   
-- Run the application: TODO
+
+**For each service** (`postgres`, `mongo`)
+declared in the *Docker Compose* configuration file
+(`docker-compose.yaml`), *Docker Compose*:
+
+1. downloads the Docker image (if not cached yet) from the Docker Hub registry,
+2. stores the downloaded image in the local Docker image cache,
+3. starts a Docker container based on this image (if it is not already running).
+
+## Stop the Application
+
+This stops all the Docker services for the application:
+
+  ```shell
+  docker compose down
+  ```
+
+
+### Docker Terminology
+
+I use ** Docker Compose** (a CLI tool) to describe and handle the lifecycle of services that comprise my application.
+
+A **service** is basically a component of the application packaged as a Docker container.
+It specifies the Docker image and version, configuration, and the network and Docker volume(s) if any.
+
+A Docker image is pre-packaged piece of software that can work as a standalone on Linux. 
+**Docker Hub** is a  public registry that hosts and serves public Docker images.
+
+
+### Postgres Service
+
+#### Start Postgres
+
+Running the app using `docker compose up -d` 
+starts **all** the application services, including `postgres`.
+
+To only start the `postgres` service:
+
+```shell
+docker compose start -d postgres
+docker compose logs postgres
+```  
+> [!NOTE]
+> 
+> The above command downloads, installs the `postgres` Docker image
+> specified by the `postgres` service in `docker-compose.yaml`.
+> Then it runs a Docker container with this image.
+
+> [!NOTE]  
+> A Docker init script automatically **creates the database user and the application database**
+> when the **`postgres`** service is run **for the first time**.
+
+Now, check that `postgres` is running:
+
+```shell
+docker compose ps | grep postgres
+```
+
+> To recreate the database, and start from scratch you need to stop the `postgres` container 
+> and remove the (data) volumes.   
+> See the `Remove all Posgres Databases` section for details.    
+
+#### Stop Postgres
+
+```shell
+docker compose stop postgres
+```
+
+#### Remove all Postgres Databases
+
+Stops and remove the `postgres` container and its data volume.
+
+> [!CAUTION]
+> This is a **destructive command** that will **remove all the databases 
+> (structure and content)** created by Postgres running in the container.
+
+```shell
+docker compose stop postgres  # Stop the container
+docker rm           postgres  # Remove the container
+docker volume rm    pg_data   # Remove the named volume 
+```
+
+
+### Mongo Service
+
+#### Start MongoDB
+
+```shell
+docker compose start mongo
+```
+
+Now, check that `mongo` is running:
+
+```shell
+docker compose ps | grep mongo
+```
+
+#### Stop MongoDB
+
+```shell
+docker compose stop mongo
+```
+
+#### Remove MongoDB and its Databases
+
+> [!CAUTION]
+> This **destructive command** will stop and remove the container, then **remove** its data **volume** 
+> (all the databases created by MongoDB running in the container).
+
+```shell
+docker compose stop mongo # Stop container
+docker  rm          mongo # Remove the stopped container
+docker volume rm    learn-dev_mongo_data # Remove the named volume   
+```
 
 
 ## Project Status
diff --git a/docker-compose.yaml b/docker-compose.yaml
index 15be136..634038c 100644
--- a/docker-compose.yaml
+++ b/docker-compose.yaml
@@ -1,24 +1,52 @@
 services:
 
-  db:
+  postgres:
     image: postgres:17
-    container_name: learn-dev-postgres
-
-    # Inject database credentials and config (db name, db user,
-    # and host port mapping) into the container.
-    # Reads from the same .env file passed to `docker compose --env-file ...`.
+    # Inject into the container the database credentials and configuration variables defined in the .env file
+    #  (database names , database user, host and port mappings)
+    #  as environment variables.
+    # This is required for the docker init script in ./docker/init/.
     env_file:
       - .env
-
+    networks:
+      - net
     volumes:
       # Init scripts: run once on first container start (empty data dir).
       - ./docker/init:/docker-entrypoint-initdb.d
       # Named volume: preserves data across container stop/start cycles.
-      - pgdata:/var/lib/postgresql/data
-
+      - pg_data:/var/lib/postgresql/data
     ports:
       # See src/main/resources/.env.example for details
       - "${POSTGRES_HOST}:${POSTGRES_PORT}:5432"
 
+  mongo:
+    image: mongo:8.0
+    restart: unless-stopped
+    ports:
+      - "${MONGO_HOST}:${MONGO_PORT}:27017"
+    environment:
+      MONGO_INITDB_ROOT_USERNAME: ${MONGO_ROOT_USERNAME}
+      MONGO_INITDB_ROOT_PASSWORD: ${MONGO_ROOT_PASSWORD}
+      MONGO_INITDB_DATABASE:      ${LEARNDEV_MONGO_DB_NAME}
+    volumes:
+      - mongo_data:/data/db
+      - ./docker/mongo/init:/docker-entrypoint-initdb.d:ro
+    networks:
+      - net
+    healthcheck:
+      test: ["CMD", "mongosh", "--quiet", "--eval", "db.adminCommand('ping').ok"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 20s
+
+networks:
+  net:
+    # A bridge network connects your services together
+    # on an isolated Virtual LAN managed by Docker.
+    driver: bridge
+
+# Named volumes used to preserve data across container stop/start cycles.
 volumes:
-  pgdata:
+  pg_data:
+  mongo_data:
diff --git a/docker/mongo/init/.gitkeep b/docker/mongo/init/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/src/main/resources/application.yaml b/src/main/resources/application.yaml
index bc4f532..905dfb2 100644
--- a/src/main/resources/application.yaml
+++ b/src/main/resources/application.yaml
@@ -2,6 +2,11 @@ spring:
   application:
     name: learn-dev
 
+  data:
+    mongodb:
+      # uri: mongodb://admin:admin_password@127.0.0.1:27018/learndev?authSource=admin
+      uri: mongodb://${MONGO_ROOT_USERNAME}:${MONGO_ROOT_PASSWORD}@${MONGO_HOST}:${MONGO_PORT}/${LEARNDEV_MONGO_DB_NAME}?authSource=admin
+
   # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   # Database Connection Configuration
   # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~