“What are chromosomes? And what does it mean to treat them as visual objects?” asks Soraya de Chadarevian in her new book, Heredity Under the Microscope: Chromosomes and the Study of the Human Genome (University of Chicago Press, 2020). Considering this question as she follows the history of microscope-based practices in chromosomal research across a variety of contexts—from the medical clinic to the study of human variation—de Chadarevian offers readers a new history of postwar human genetics. This approach enables her to argue that cytogenetics was far from just “old fashioned biology that was eventually superseded by molecular approaches” and to show the continuities and interdependencies between different methods for studying our DNA. Learn more about your ad choices. Visit megaphone.fm/adchoices