diff --git a/notes/chap6_objects.md b/notes/chap6_objects.md
index 84a4289..91f5016 100644
--- a/notes/chap6_objects.md
+++ b/notes/chap6_objects.md
@@ -442,6 +442,24 @@ merge({x: 1}, {x: 2, y: 2}, {y: 3, z: 4})          // => {x: 1, y: 2, z: 4}
 
 ## 6.8 Serializing Objects
 
+**Object serialization** = process to convert an object's state to a string. Then later we can restore it.
+
+2 functions:
+* `JSON.stringify()`: serialize JS objects.
+* `JSON.parse`: restore JS objects.
+
+JSON stands for **"JavaScript Object Notation"**
+```js
+let o = {x: 1, y: {z: [false, null, ""]}}; // Define a test object
+let s = JSON.stringify(o);   // s == '{"x":1,"y":{"z":[false,null,""]}}'
+let p = JSON.parse(s);       // p == {x: 1, y: {z: [false, null, ""]}}
+```
+
+What can/cannot be serialized?
+* CAN be serialized: Objects, arrays, strings, finite numbers, `true`, `false`, `null`
+  * `NaN`, `Infinity`, `-Infinity` serialized to `null`
+* CANNOT be serialized: Function, RegExp, Error objects, `undefined` value
+
 ## 6.9 Object Methods
 
 ### 6.9.1 The toString() Method