The graph controller allows you to view your graph even closer. The controller bar below the graph allows you to zoom into a specific region and pan across the data easily. This is especially useful if you are viewing more than one day's worth of glucose data.
You can tap the square icon in the top right corner of the graph to open a full-screen version. While zoomed in, you can still change the graph date. If you hover over a meal, you can see the photo and description of that meal directly in the callout area, under the glucose number.