diff --git a/src/cristallina/utils.py b/src/cristallina/utils.py
index 138c447..86c2059 100644
--- a/src/cristallina/utils.py
+++ b/src/cristallina/utils.py
@@ -380,7 +380,8 @@ class ROI:
 
     Example: ROI(left=10, right=20, bottom=100, top=200).
 
-    Directions assume that lower left corner of image is at (x=0, y=0).
+    Directions assume that lower left corner of image is at (x=0, y=0)
+    and y is pointing upwards, x pointing to the right.
     """
 
     def __init__(
@@ -457,7 +458,7 @@ class ROI:
         """ Returns a new ROI that is shifted 
             by x to the left and by y pixels up.
             
-            If `inplace=True` shifts the existing ROI instead.
+            If `inplace=True` shifts the itself instead.
          """
         if not inplace:
             return ROI(left=self.left+x, 
@@ -472,6 +473,26 @@ class ROI:
             self.top = self.top + y
 
 
+    def expand(self, x: float, y: float, inplace=False):
+        """ Returns a new ROI that is expanded in x 
+            to the left and right, and in y to the 
+            top and bottom.        
+            
+            If `inplace=True` expands the itself instead.
+        """
+        if not inplace:
+            return ROI(left=self.left - x, 
+                    right=self.right + x, 
+                    bottom = self.bottom - y,
+                    top=self.top + y,
+                    name=self.name)
+        else:
+            self.left = self.left - x
+            self.right = self.right + x
+            self.bottom = self.bottom - y
+            self.top = self.top + y
+
+
     def __repr__(self):
         if hasattr(self, "name"):
             return f"ROI(bottom={self.bottom},top={self.top},left={self.left},right={self.right},name='{self.name}')"