diff --git a/4_integration_clustering.qmd b/4_integration_clustering.qmd
index 5a27643..d279ce0 100644
--- a/4_integration_clustering.qmd
+++ b/4_integration_clustering.qmd
@@ -34,7 +34,7 @@ VariableFeatures(seu) <- intersect(VariableFeatures(seu_list$Anterior),
 ::: {.callout-important}
 ## Exercise
 
-How many variable features do we have? We did we select fewer genes than the default (check `?VariableFeatures`)?
+How many variable features do we have? Why did we select fewer genes than the default (check `?VariableFeatures`)?
 
 ::: 
 
diff --git a/assets/images/mouse_brain_sagittal.png b/assets/images/mouse_brain_sagittal.png
index 685f79e..22865f7 100644
Binary files a/assets/images/mouse_brain_sagittal.png and b/assets/images/mouse_brain_sagittal.png differ
diff --git a/precourse_preparations.qmd b/precourse_preparations.qmd
index 14ee234..087fc13 100644
--- a/precourse_preparations.qmd
+++ b/precourse_preparations.qmd
@@ -2,8 +2,6 @@
 title: "Precourse preparations"
 ---
 
-Audience and requirements
-
 The target audience are researchers that are interested to analyse spatial transcriptomics datasets. Attendees should have basic understanding of:
 
 - The programming language R