diff --git a/README.md b/README.md
index 632b4c2..3662f50 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,9 @@
 # xoptics
 
+Change Athos energy (in eV) via the undulators
+
+```bash
+SetAthosUndEnergy.sh 567
+```
+
+