Given how much time modern people spend indoors or in public transport, American biologist Rob Dunn argues that we know unforgivably little about our closest neighbors and their impact on our well-being. To remedy this omission, Rob Dunn is leading a research team to "inventory" the life forms in and around our homes. As it turned out, these are many hundreds of thousands of species. These include vertebrates, plants, arthropods, fungi, and bacteria. Which species are dangerous for us, and which are necessary? The author of the book advocates for biodiversity and proves its necessity not only in the wild, but also in our homes. How can the disappearance of one butterfly species in one area cause an increase in allergic diseases? Why do Finnish Karelians, unlike Russian ones, more often suffer from allergic diseases? How to get rid of black mold? Why does fighting cockroaches often only harden them and make them even more resilient? How do bacteria on a baker's hands affect the taste of bread and what are the benefits of fermented foods? Who lives in the shower head and is it urgently necessary to change it? The discoveries made by Dunn became a revelation for him. The reader has them ahead of them.