There are various ways that you can use to focus very close to small subjects. Here is a list of choices.
Macro Lenses. You can purchase a lens that is specifically designed to focus closely. These are called “macro” lenses, and they are available in focal lengths between 50mm and 200mm (figure A). They can also focus to infinity so you can use them for landscapes, portraits, etc., but photographers buy them primarily to use in close-up work.