A kitten doesn’t come into the world with a ready immune system — it builds one, piece by piece, starting with something as tiny as bacteria. When a kitten is born, it’s a blank slate — sterile, untouched by the outside world. But almost immediately, something beautiful happens. As it nurses, is licked clean, and nestles up against its mother, she shares with it a whole invisible world of microbes. Researchers like Chan et al. (2013) and Zakošek Pipan et al. (2020) have descr