diff --git a/README.md b/README.md
index 8b6e1f4..50b0969 100644
--- a/README.md
+++ b/README.md
@@ -103,6 +103,7 @@ Currently, there are these translations of **wtfjs**:
   - [Same variable redeclaration](#same-variable-redeclaration)
   - [Default behavior Array.prototype.sort()](#default-behavior-arrayprototypesort)
   - [resolve() won't return Promise instance](#resolve-wont-return-promise-instance)
+  - [```{}{}``` is undefined](#user-content--is-undefined)
 - [📚 Other resources](#-other-resources)
 - [🎓 License](#-license)
 
@@ -1733,9 +1734,40 @@ thePromise.then(value => {
 
 > This function flattens nested layers of promise-like objects (e.g. a promise that resolves to a promise that resolves to something) into a single layer.
 
-– [Promise.resolve() on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve)
+- [Promise.resolve() on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/resolve)
 
 The specification is [ECMAScript 25.6.1.3.2 Promise Resolve Functions](https://tc39.es/ecma262/#sec-promise-resolve-functions). But it is not quite human-friendly.
+ 
+## `{}{}` is undefined
+
+Write them in console. They will return the value that defined in last object.
+
+```
+{}{}; // undefined
+{}{}{}; // undefined
+{}{}{}{}; // undefined
+{foo: 'bar'}{}; // 'bar'
+{}{foo: 'bar'}; // 'bar'
+{}{foo: 'bar'}{}; // 'bar'
+{a: 'b'}{c:' d'}{}; // 'd'
+{a: 'b', c: 'd'}{}; // SyntaxError: Unexpected token ':'
+({}{}); // SyntaxError: Unexpected token '{'
+```
+
+### 💡 Explanation:
+
+When inspecting each ```{}```, they returns undefined. If you inspect ```{foo: 'bar'}{}```, you will find ```{foo: 'bar'}``` is ```'bar'```.
+
+There are 2 meaning for {}: object and block.
+For example, the {} in ()=>{} means block. So we need to use ()=>({}) to return an object.
+
+Let's use ```{foo: 'bar'}``` as a block. Write this snippet in your console:
+
+```
+if(true) {foo: 'bar'} // 'bar'
+```
+
+Surprisingly, it behaviors the same! You can guess here that ```{foo: 'bar'}{}``` is a block.
 
 # 📚 Other resources