The chapter where you can find this episode in the book is Chapter 31. It is entitled “Hela, Goddess of Death.” In the chapter, Rebecca Skloot and Henrietta’s daughter Deborah take Deborah’s grandsons, Alfred and Davon, to the Maryland Science Center. There, the boys see a picture of cells as seen in a microscope. The picture covers the entire twenty-foot wall. The boys wonder if the cells might be from their great-grandmother and are very excited to hear that they might be.
For whatever reason, the phrase “Maryland Science Center” does not appear in the index of the book. One thing that you can do when this sort of thing happens is to use Google Books or Amazon and search for a particular word or phrase. That can help you find the passage you are looking for if you cannot use the index.
So, the chapter you are looking for is Chapter 31.