diff --git a/documentation/ref-manual/ref-classes.xml b/documentation/ref-manual/ref-classes.xml
index 92d2af110f..99e9edb69b 100644
--- a/documentation/ref-manual/ref-classes.xml
+++ b/documentation/ref-manual/ref-classes.xml
@@ -28,6 +28,15 @@
     default behaviour.
 </para>
 
+<para>
+    This chapter discusses only the most useful and important classes.
+        Other classes do exist within the <filename>meta/classes</filename>
+        directory in the
+        <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
+        You can reference the <filename>.bbclass</filename> files directly
+        for more information.
+</para>
+
 <section id='ref-classes-base'>
     <title>The base Class - <filename>base.bbclass</filename></title>