diff --git a/intro.md b/intro.md
index d2e1203..e15f2c3 100644
--- a/intro.md
+++ b/intro.md
@@ -1,12 +1,19 @@
 # Introduction to Bitcoin
 
-Lesson 1: [What is Bitcoin like? Using analogies to understand Bitcoin](analogies.md)
-Lesson 2: [The 5 meme principles of Bitcoin. To dos and not to dos](principles.md)
-Lesson 3: [FAQ](faq.md)
+## Theory
+
+- Lesson 1: [What is Bitcoin like? Using analogies to understand Bitcoin](analogies.md)
+- Lesson 2: [The 5 meme principles of Bitcoin. To dos and not to dos](principles.md)
+- Lesson 3: [FAQ](faq.md)
+
+## Mobile phone wallet
+
 Lesson 4: [Using a mobile phone wallet, setup](bluewallet_setup.md)
 Lesson 5: [Using a mobile phone wallet, recovery](bluewallet_recovery.md)
 Lesson 6: [Using a mobile phone wallet, buying bitcoin](bluewallet_buying.md)
 Lesson 7: [Using a mobile phone wallet, sending bitcoin](bluewallet_sending.md)
+
+## Hardware wallet
 Lesson 8: [Using a hardware wallet, setup](ledger_setup.md)
 Lesson 9: [Using a hardware wallet, recovery](ledger_recovery.md)
 Lesson 10: [Using a hardware wallet, buying bitcoin](ledger_buying.md)