diff --git a/README.md b/README.md
index 3a81b53..bdd805e 100644
--- a/README.md
+++ b/README.md
@@ -76,6 +76,10 @@ dokku mysql:link lolipop playground
 #   DATABASE_PORT_3306_TCP_PORT=3306
 #   DATABASE_PORT_3306_TCP_ADDR=172.17.0.1
 
+# you can examine the environment variables
+# using our 'playground' app's env command
+dokku run playground env
+
 # you can customize the environment
 # variables through a custom docker link alias
 dokku mysql:alias lolipop MYSQL_DATABASE