diff --git a/Prog/Collections.md b/Prog/Collections.md
index 9dc58d8..34b2cd5 100644
--- a/Prog/Collections.md
+++ b/Prog/Collections.md
@@ -1 +1,16 @@
 We have 3 collections namespace in C#
+- System.Collections
+	- Store items as Object
+	- ArrayList
+	- Queue
+	- Stack
+	- Hashtable
+- System.Collections.Generic
+	- Using Generics to specify one data type
+	- List
+	- Queue
+	- Stack
+	- Dictionary<TKey,TValue>
+- System.Collections.Concurrent
+	- As previous bu thread safe
+- 
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