diff --git a/Smart-Contract-Security/reentrancy-notes.md b/Smart-Contract-Security/reentrancy-notes.md
index fcbc2f4..3f356e4 100644
--- a/Smart-Contract-Security/reentrancy-notes.md
+++ b/Smart-Contract-Security/reentrancy-notes.md
@@ -1 +1,18 @@
-## Notes on Reentrancy
+## Reentrancy
+
+
+<br>
+
+* When a contract calls an external function, that external function may itself call the calling function.
+* To prevent this attack, a contract can implement a lock in storage that prevents re-entrant calls.
+
+<br>
+
+### References to learn about reentrancy
+
+<br>
+
+* [Solidity docs](https://docs.soliditylang.org/en/latest/security-considerations.html#re-entrancy)
+* [DASP](https://www.dasp.co/#item-1)
+* [SWC](https://swcregistry.io/docs/SWC-107)
+* [Not so smart contract](https://github.com/crytic/not-so-smart-contracts/tree/master/reentrancy)