Back Story:
After several delays on January 28, 1986, Shuttle Challenger launched. In the second minute of its departure, the shuttle exploded/disintegrated. In retrospect, scientists were able to discern that extreme damage to the O rings were the root cause for the explosion.
That morning, engineers from Thiokol and NASA managers exchanged information regarding the launch. The engineers, based on their data, felt that it was unsafe to launch. Over 10 charts and graphs were sent between the two groups, the engineers desperately attempting to convince the NASA managers of their concerns. Below is an example of the types of visual information Thiokol sent over:

My smart and kind professor, Nancy Kaplan brought to the class' attention that the "story" Thiokol was trying to tell was not being properly revealed. What is their point in this graph? It's difficult to say. Thiokol didn't presenta strong enough argument about the dangers of the flight, and the NASA managers gave the go ahead that led to disaster.
DaVinci of Data:
Years later, enter the "daVinci of data" as the NYTimes calls him, Edward Tufte (hello, new nerd crush, this guy's work is awesome!)
Edward Tufte is renowned for taking data and turning them into visual displays that are one, and most importantly, conherent and bursting with vital information and two, beautiful.
Visual heirarchy:
He took the information that was sent between the Thiokol engineers and Nasa managers and reworked them. He figured out what was important and what was less so. Here's the graph that Tufte came up with:

I apologize for the low resolution. But the y axis is "amount of damage in O ring", and the x axis is "temperature increasing." And it becomes VERY OBVIOUS, with the data they have, that as the temperature goes down the O rings damage increases.
The data points are from like 53 degrees F to 84 degrees F, roughly. At the lowest recorded temperature, 53 degrees, they recorded the most damage to an O ring (level 4). This being the case---how could you launch a shuttle when it was only 26 degrees F outside?
The graph shows the "story" clearly and immediately. Good design saves lives. Tell that story the next time a lousy client belittles the significance of your profession.