Superior design means getting little details right — even the parts that no one can see. In his landmark biography of Steve Jobs, Walter Isaacson tells the story of Jobs’s obsession to detail in the design of the breakthrough Apple II personal computer, down to the engineering of the power supply inside the computer. Jobs wanted the Apple II to provide power without needing to use a fan inside the unit because he believed fans were distracting. So he hired an engineer named Rod Holt, who created a new power system that was more efficient and superior to a fan-based supply. Isaacson writes:

Jobs’s father had once taught him that a drive for perfection meant caring about the craftsmanship even of the parts unseen. Jobs applied that to the layout of the circuit board inside the Apple II. He rejected the initial design because the lines were not straight enough.

One of my favorite examples of designing the unseen details comes from Outpost Trading Company, which created this Beatles T shirt that depicts A Hard Day’s Night:

The design really gets interesting on the inside, which no one but the owner can see. Beneath the Outpost Trading Company label is an awesome silhouette of the iconic Abbey Road album cover:

The discerning eye might note that the Beatles look like they are walking the wrong way, going from the right side to the left, instead of the left-right sequence depicted on the album cover. But when you wear the T-shirt, the Beatles are walking left to right as they did on the cover — unseen to anyone, like a private joke shared with the shirt wearer.

The unseen details make the difference between an ordinary product and a special experience that rewards the buyer with a more personalized feel. Unseen details also create curiosity: I definitely want to learn more about Outpost Trading Company in addition to admiring the T shirt. Unseen details also send a message to customers: our brand trusts you. We trust you to take the time to notice something subtle about our product, and we trust that you’ll appreciate the effort we have taken to go the extra mile and do something other brands might not do.

These little details are often associated with premium products and services such as gourmet dining. But any kind of brand can embed unseen details in its products and services to achieve surprise and delight, as fast-food chain In-n-Out Burger has done with its “Secret Menu.” The Secret Menu originally consisted of custom-made food orders off the menu, available only if you knew to ask for them. The Secret Menu eventually became not very secret, but the concept still helps In-n-Out Burger position itself as a hip, even cult brand.

What are your favorite examples of unseen design?