Joe Polchinski, based at the Kavli Institute for Theoretical Physics in Santa Barbara, is one of the world’s leading string theorists and an avid cyclist. (Many colleagues have challenged him to a race, to their later chagrin.) He is best known for showing that string theory isn’t just about strings—it predicts a huge diversity of structures going under the general rubric of “branes” (short for membranes). Here he describes how spacetime might dissolve on microscopic scales, a theme that I develop in Chapter 5 of my book. The filmmaker is Gary Smaby, who was an artist-in-residence at KITP at the same time I was the writer-in-residence there, in 2012.