As more and more pictures are saved digitally, a new exhibition at the Met aims to celebrate the powerful nostalgia and sentiment that a physical photograph can evoke. “Don’t Forget to Call Your Mother,” which takes its title from a photograph by Maurizio Cattelan, displays film stills and photos from the museum’s collection going back to the 1970s. Featuring artists such as Sadie Barnette, Sophie Calle, and Darrell Ellis, the show uses photographs as objects that tell a larger story, exploring how people are shaped by childhood, and how a better understanding of the past can help decipher the present. —Alice Browne