Continuing with our analogy, let's say we're looking for the phrase Ada Lovelace in a paragraph. Ada Lovelace was a mathematician and writer who lived in the 19th century. And she holds the honor of having published the very first algorithm intended to be used by a machine to perform calculations, which makes her the first ever computer programmer. In the first layer of the network, a CNN looks for the basic building blocks of an image. The basic building blocks of written language are letters. So in this analogy, the filters the CNN uses in the first layer would be letters.