diff --git a/_includes/package-nav.html b/_includes/package-nav.html
index 1bac99d..7e5147e 100644
--- a/_includes/package-nav.html
+++ b/_includes/package-nav.html
@@ -1,15 +1,22 @@
 <li><a href="intro.html">Introduction</a></li>
+
+<li class="dropdown-header">Data science essentials</li>
 <li><a href="visualize.html">Visualize</a></li>
+<li><a href="rmarkdown.html">R Markdown</a></li>
 <li><a href="transform.html">Transform</a></li>
-<li><a href="strings.html">String manipulation</a></li>
-<!--
-<li><a href="dates.html">Dates and times</a></li>
--->
 <li><a href="tidy.html">Tidy</a></li>
-<li><a href="expressing-yourself.html">Expressing yourself</a></li>
 <li><a href="import.html">Import</a></li>
+
+<li class="dropdown-header">Programming</li>
+<li><a href="data-structures.html">Data structures</a></li>
+<li><a href="strings.html">Strings</a></li>
+<li><a href="datetimes.html">Dates and times</a></li>
+<li><a href="functions.html">Expressing yourself with code</a></li>
 <li><a href="lists.html">Lists</a></li>
-<!--
-<li><a href="models.html">Model</a></li>
-<li><a href="communicate.html">Communicate</a></li>
--->
+<li><a href="shiny.html">Shiny</a></li>
+
+<li class="dropdown-header">Modelling</li>
+<li><a href="model-linear.html">Linear models</a></li>
+<li><a href="model-vis.html">Models and visualisation</a></li>
+<li><a href="model-assess.html">Model assesment</a></li>
+<li><a href="model-other.html">Other models</a></li>
diff --git a/data-structures.Rmd b/data-structures.Rmd
new file mode 100644
index 0000000..181e7c8
--- /dev/null
+++ b/data-structures.Rmd
@@ -0,0 +1,21 @@
+---
+layout: default
+title: Data structures
+output: bookdown::html_chapter
+---
+
+Might be quite brief.
+
+## Data structures
+
+Atomic vectors and lists. What is a data frame?
+
+`typeof()` vs. `class()` mostly in context of how date/times and factors are built on top of simpler structures.
+
+## Factors
+
+(Since won't get a chapter of their own)
+
+## Subsetting
+
+Not sure where else this should be covered.
diff --git a/datetimes.Rmd b/datetimes.Rmd
new file mode 100644
index 0000000..0d375dc
--- /dev/null
+++ b/datetimes.Rmd
@@ -0,0 +1,5 @@
+---
+layout: default
+title: Dates and times
+output: bookdown::html_chapter
+---
diff --git a/expressing-yourself.Rmd b/functions.Rmd
similarity index 100%
rename from expressing-yourself.Rmd
rename to functions.Rmd
diff --git a/modelling.Rmd b/model-assess.Rmd
similarity index 98%
rename from modelling.Rmd
rename to model-assess.Rmd
index 2db7755..80c955d 100644
--- a/modelling.Rmd
+++ b/model-assess.Rmd
@@ -1,6 +1,6 @@
 ---
 layout: default
-title: Modelling
+title: Models assessment
 output: bookdown::html_chapter
 ---
 
diff --git a/model-linear.Rmd b/model-linear.Rmd
new file mode 100644
index 0000000..15f52ea
--- /dev/null
+++ b/model-linear.Rmd
@@ -0,0 +1,20 @@
+---
+layout: default
+title: Model
+output: bookdown::html_chapter
+---
+
+# Model
+
+After reading this chapter, what can you do that you couldn't before?
+
+Focus on fitting a single model, and understanding it with broom. Focus on linear models. Focus on intutition and computation tools. No mathematics.
+
+Review caret and mlr.
+
+"Feature engineering":
+
+* Factors
+* Interactions
+* Splines
+* Log transform
diff --git a/model-other.Rmd b/model-other.Rmd
new file mode 100644
index 0000000..f16857c
--- /dev/null
+++ b/model-other.Rmd
@@ -0,0 +1,14 @@
+---
+layout: default
+title: Other model familes
+output: bookdown::html_chapter
+---
+
+
+## Extensions of linear models
+
+* Generalised linear models: logistic, ...
+
+* Hierarchical models
+
+## 
diff --git a/model-vis.Rmd b/model-vis.Rmd
new file mode 100644
index 0000000..430cb51
--- /dev/null
+++ b/model-vis.Rmd
@@ -0,0 +1,7 @@
+---
+layout: default
+title: Models and visualisation
+output: bookdown::html_chapter
+---
+
+Gap minder
diff --git a/rmarkdown.Rmd b/rmarkdown.Rmd
new file mode 100644
index 0000000..2016e17
--- /dev/null
+++ b/rmarkdown.Rmd
@@ -0,0 +1,5 @@
+---
+layout: default
+title: R Markdown
+output: bookdown::html_chapter
+---
diff --git a/shiny.Rmd b/shiny.Rmd
new file mode 100644
index 0000000..c32a30f
--- /dev/null
+++ b/shiny.Rmd
@@ -0,0 +1,5 @@
+---
+layout: default
+title: Shiny
+output: bookdown::html_chapter
+---
diff --git a/transform.Rmd b/transform.Rmd
index f0a5bc0..cb9f2ea 100644
--- a/transform.Rmd
+++ b/transform.Rmd
@@ -4,18 +4,24 @@ title: Data transformation
 output: bookdown::html_chapter
 ---
 
-# Data transformation
+Copy from dplyr vignettes.
 
-## Missing values
+## Filter
+
+### Missing values
 
 * Why `NA == NA` is not `TRUE`
 * Why default is `na.rm = FALSE`.
 
-## Data types
+## Mutate
 
-Overview of different data types and useful summary functions for working with them. Strings and dates covered in more detail in future chapters.  
+## Arrange
 
-Need to mention `typeof()` vs. `class()` mostly in context of how date/times and factors are built on top of simpler structures.
+## Select
+
+## Grouped summaries
+
+Overview of different data types and useful summary functions for working with them. Strings and dates covered in more detail in future chapters.   Anything complicated can be put off until data structures chapter.
 
 ### Logical
 
@@ -26,3 +32,5 @@ When used with numeric functions, `TRUE` is converted to 1 and `FALSE` to 0. Thi
 ### Strings (and factors)
 
 ### Date/times
+
+## Grouped mutate