have billions of pixels in my cellphone, and you probably do too. But what is a pixel? Why do so many people think that pixels are little abutting squares? Now that we’re aswim in an ocean of zettapixels (21 zeros), it’s time to understand what they are. The underlying idea – a repackaging of infinity – is subtle and beautiful. Far from being squares or dots that ‘sort of’ approximate a smooth visual scene, pixels are the profound and exact concept at the heart of all the images that surround us – the elementary particles of modern pictures.