diff --git a/School/Analyse/Layers/1. Physical Layer.md b/School/Analyse/Layers/1. Physical Layer.md
index 1d4cb20..5d6301b 100644
--- a/School/Analyse/Layers/1. Physical Layer.md	
+++ b/School/Analyse/Layers/1. Physical Layer.md	
@@ -119,4 +119,10 @@ This is also called signal to noise ratio (SNR)
 ## Transmission Media
 These signals are send through a transmission medium.  A transmission medium is a physical object that can carry the information from source to destination.
 
-Transmission mediums are often space (air), metallic cable or fibv
\ No newline at end of file
+Transmission mediums are often space (air), metallic cable or fiber optic cables.
+
+Transmission media are divided in 2 groups.
+
+### Guided media
+
+### Unguided media
\ No newline at end of file