diff --git a/docs/source/application_layers.rst b/docs/source/application_layers.rst
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+Application Layers
+==================
+
+This project can be understood in two documentation levels:
+
+* **UI layer**: templates, static assets, and page-level interactions that users see.
+* **Backend layer**: Django views, forms, models, routing, and risk computation logic.
+
+UI Layer
+--------
+
+The UI is server-rendered with Django templates and enhanced with JavaScript snippets embedded in template partials.
+
+Key entry points
+~~~~~~~~~~~~~~~~
+
+* `qmra/templates/layout.html` provides the shared shell (page frame) for most pages.
+* `qmra/templates/index.html` is the public landing page.
+* `qmra/risk_assessment/templates/assessment-configurator.html` is the main guided workflow for creating a risk assessment.
+* `qmra/risk_assessment/templates/assessment-result.html` presents simulation outputs and charts.
+* `qmra/user/templates/*.html` handles authentication and account-facing screens.
+
+UI building blocks
+~~~~~~~~~~~~~~~~~~
+
+* **Global styling** is defined in `qmra/static/css/styles.css`.
+* **Images/icons** are served from `qmra/static/img/`.
+* **Dynamic form behavior** is placed in template fragments such as:
+
+  * `qmra/risk_assessment/templates/inflows-form-js.html`
+  * `qmra/risk_assessment/templates/treatments-form-js.html`
+  * `qmra/risk_assessment/templates/risk-assessment-form-js.html`
+
+Typical UI flow
+~~~~~~~~~~~~~~~
+
+1. User opens the configurator page.
+2. User selects/creates inflows, treatments, and exposure settings.
+3. User submits the form.
+4. Backend computes Monte Carlo outcomes.
+5. Results page renders plots and export options.
+
+Backend Layer
+-------------
+
+The backend is a Django application split into project-level wiring and feature apps (`risk_assessment` and `user`).
+
+Project-level backend
+~~~~~~~~~~~~~~~~~~~~~
+
+* `qmra/settings.py` contains Django configuration.
+* `qmra/urls.py` maps root URL patterns to app routes.
+* `qmra/views.py` contains project-level views (e.g., landing page).
+* `manage.py` is the command entrypoint for local operations.
+
+Risk assessment domain backend
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+* `qmra/risk_assessment/models.py` stores persisted domain entities.
+* `qmra/risk_assessment/qmra_models.py` defines QMRA reference data structures used by the simulation logic.
+* `qmra/risk_assessment/forms.py` validates and structures UI submissions.
+* `qmra/risk_assessment/views.py` implements the request/response workflow for configurator, results, and CRUD operations.
+* `qmra/risk_assessment/risk.py` executes core risk calculations and simulation logic.
+* `qmra/risk_assessment/plots.py` prepares data visualizations returned to templates.
+* `qmra/risk_assessment/exports.py` handles export generation for assessment results.
+* `qmra/risk_assessment/urls.py` exposes risk-assessment routes.
+
+User/account backend
+~~~~~~~~~~~~~~~~~~~~
+
+* `qmra/user/models.py` contains user-facing data models.
+* `qmra/user/views.py` handles registration, login-related pages, and account actions.
+* `qmra/user/urls.py` defines account URL patterns.
+
+Data bootstrap and operations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+* `qmra/management/commands/seed_default_db.py` loads default entities.
+* `qmra/management/commands/collect_static_default_entities.py` snapshots configured defaults into static JSON.
+* `qmra/management/commands/export_default.py` exports default data sets.
+* `qmra/static/data/*.json` stores default inflow, pathogen, treatment, source, reference, and exposure datasets consumed by backend workflows.
+
+Request lifecycle (high-level)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+1. URL dispatch in `qmra/urls.py` or app `urls.py` selects a view.
+2. View instantiates forms, loads defaults/database entities, and validates input.
+3. Risk logic in `risk.py` and helper modules computes outputs.
+4. View sends context to templates for HTML rendering (and optional exports).
diff --git a/docs/source/index.rst b/docs/source/index.rst
index cd3c1f9..804d29d 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -5,6 +5,7 @@ Welcome to QMRA's documentation!
    :maxdepth: 2
    :caption: Contents:
 
+   application_layers
 
 QMRA is a Django project which experiments with deploying state-of-the-art techniques 
 for Quantitative Microbial Risk Assessment (QMRA).