diff --git a/contracts/crowdsale/Crowdsale.sol b/contracts/crowdsale/Crowdsale.sol
index d4578ec4e..1667b4bb5 100644
--- a/contracts/crowdsale/Crowdsale.sol
+++ b/contracts/crowdsale/Crowdsale.sol
@@ -25,7 +25,10 @@ contract Crowdsale {
   // Address where funds are collected
   address public wallet;
 
-  // How many token units a buyer gets per wei
+  // How many token units a buyer gets per wei.
+  // The rate is the conversion between wei and the smallest and indivisible token unit.
+  // So, if you are using a rate of 1 with a DetailedERC20 token with 3 decimals called TOK
+  // 1 wei will give you 1 unit, or 0.001 TOK.
   uint256 public rate;
 
   // Amount of wei raised
diff --git a/contracts/token/ERC20/DetailedERC20.sol b/contracts/token/ERC20/DetailedERC20.sol
index 749d96071..e4918533a 100644
--- a/contracts/token/ERC20/DetailedERC20.sol
+++ b/contracts/token/ERC20/DetailedERC20.sol
@@ -3,6 +3,12 @@ pragma solidity ^0.4.23;
 import "./ERC20.sol";
 
 
+/**
+ * @title DetailedERC20 token
+ * @dev The decimals are only for visualization purposes.
+ * All the operations are done using the smallest and indivisible token unit,
+ * just as on Ethereum all the operations are done in wei.
+ */
 contract DetailedERC20 is ERC20 {
   string public name;
   string public symbol;