When the poet Robin Coste Lewis discovered a trove of photographs under her late grandmother’s bed, she recognized them not only as a document of her family’s history during the Great Migration, but also as a testament to Black intimacy and ingenuity across generations. From studio portraits to snapshots, tintypes to Polaroids, these pictures provide the foundation of Robin’s latest book, “To the Realization of Perfect Helplessness,” excerpts from which were published on newyorker.com. Robin Coste Lewis formerly served as poet laureate of Los Angeles, and her debut collection, “Voyage of the Sable Venus,” won the 2015 National Book Award for poetry.