diff --git a/data-visualize.qmd b/data-visualize.qmd
index 503bbb8..d8f524b 100644
--- a/data-visualize.qmd
+++ b/data-visualize.qmd
@@ -396,9 +396,11 @@ One way to add additional variables to a plot is by mapping them to an aesthetic
 Another way, which is particularly useful for categorical variables, is to split your plot into **facets**, subplots that each display one subset of the data.
 
 To facet your plot by a single variable, use `facet_wrap()`.
-The first argument of `facet_wrap()` is a formula, which you create with `~` followed by a variable name (here, "formula" is the bane if a data structure in R, not a synonym for "equation").
+The first argument of `facet_wrap()` is a formula[^data-visualize-1], which you create with `~` followed by a variable name.
 The variable that you pass to `facet_wrap()` should be discrete.
 
+[^data-visualize-1]: Here "formula" is the name of the type of thing created by `~`, not a synonym for "equation".
+
 ```{r}
 #| fig-alt: >
 #|   Scatterplot of highway fuel efficiency versus engine size of cars, 
@@ -409,9 +411,8 @@ ggplot(data = mpg) +
   facet_wrap(~cyl)
 ```
 
-To facet your plot on the combination of two variables, add `facet_grid()` to your plot call.
-The first argument of `facet_grid()` is also a formula.
-This time the formula should contain two variable names separated by a `~`.
+To facet your plot with the combination of two variables, switch from `facet_wrap()` to `facet_grid()`.
+The first argument of `facet_grid()` is also a formula, but now it's a double sided formula: `rows ~ cols`.
 
 ```{r}
 #| fig-alt: >
@@ -426,8 +427,6 @@ ggplot(data = mpg) +
   facet_grid(drv ~ cyl)
 ```
 
-If you prefer to not facet in the rows or columns dimension, use a `.` instead of a variable name, e.g. `+ facet_grid(. ~ cyl)`.
-
 ### Exercises
 
 1.  What happens if you facet on a continuous variable?