diff --git a/default_environment/stylesheet/main.css b/default_environment/stylesheet/main.css
index 9beb74d..de07c06 100644
--- a/default_environment/stylesheet/main.css
+++ b/default_environment/stylesheet/main.css
@@ -270,4 +270,11 @@ body {
   b {
     font-weight: 700;
   }
+
+  /* Never have media larger than its container */
+  img,
+  picture,
+  video {
+    max-width: 100%;
+  }
 }