The charts are not decoration; they are controls. Three moves cover almost everything you will do with them.
Drill down is clicking to go finer. On a trend chart, clicking a quarter takes you to its months, a month to its weeks, a week to its days. On a breakdown chart, clicking a segment takes you to the next level of that segment's own structure — a product category into its products, for example. You are never guessing what a total is made of: one more click always shows its parts.
Filtering the grid is where the drilling lands. When you reach the finest level and click, the grid below narrows to match: click a day on the trend and the grid shows that day's documents; click a customer on the breakdown and the grid shows that customer's documents. A bar above the grid names the filter in force — Grid filtered by … — with a Clear control that removes it. The breakdown chart always adds up to the same total as its KPI tile, so the slice you click is exactly the slice the grid shows.
Drill across leaves the cockpit entirely. Some chart points — a customer, a supplier, a product — carry a link to that record's own 360° view (see 1.4), taking the period with you. So from "revenue by customer" you can step straight into the customer's page, where the statement, the documents and the activity live. Drilling across works because every part of the analytics shares the same dimensions (see 2.8): the customer on the Sales chart is the customer on the record, and the product in Procurement is the product in Inventory.
Figure 2.2 — Drilling from a chart into the grid. Drawing to be produced after the UI/UX pass: a breakdown chart mid-drill, the "Grid filtered by" bar in place, and the narrowed grid below.