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The outside-in principle is implicit in a number of programming practices and methodologies that work at different scales. But explicitly identifying the general principle should allow you to both better understand these methodologies and extend the benefits to other areas that they don’t cover. By working through the details of details of the outer layer, you minimize the risk of having to rewrite them because of a misunderstanding about how the software will connect and interact with its external environment. An MVP (MVP) will have all the layers of a product facing facing a very narrow slice of a final product, but narrow a slice of the product before a product is a very thin slice of it.