diff --git a/doc/.$ctrl-drawings.drawio.bkp b/doc/.$ctrl-drawings.drawio.bkp
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diff --git a/doc/core-messaging.svg b/doc/core-messaging.svg
index d66156d..557ecea 100644
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+++ b/doc/core-messaging.svg
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diff --git a/doc/ctrl-drawings.drawio b/doc/ctrl-drawings.drawio
index 946c23d..ea89240 100644
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diff --git a/doc/src/core_overview.md b/doc/src/core_overview.md
index 562a737..94cf407 100644
--- a/doc/src/core_overview.md
+++ b/doc/src/core_overview.md
@@ -1,5 +1,11 @@
# Core overview
+This is just a quick introduction to the core concepts of ctrl. Details can be found by reading further in the **Core ctrl** section.
+
+## Concept
+
+In ctrl all nodes are treated equally, and there is no concept of client/server. There are just nodes that can send messages to other nodes, and the messages contains commands of what to do on the node that receives the message.
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The example that follows will scrape prometheus metrics with two ctrl nodes, deliver them to a third node called **metrics**, and expose them with the builtin http server. Prometheus can then be used to read all the metrics from the various nodes on the **metrics** node.
Before you start, make sure to read the **User Guides** section for how to start up a NATS broker, and for general information about setting up ctrl.
diff --git a/doc/usecase-prometheus-collector.svg b/doc/usecase-prometheus-collector.svg
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+++ b/doc/usecase-prometheus-collector.svg
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\ No newline at end of file