An accessory dwelling unit (ADU) is a small, self-contained living space that is built on or within the same lot as an existing single-family home. ADUs are also known as granny flats, in-law units, or secondary suites. They can be built in a variety of forms such as a basement apartment, a garage conversion, a small detached building, or even a tiny home. The purpose of an ADU is to provide additional living space for family members, renters, or guests, while maintaining the privacy of the main home. ADUs are becoming increasingly popular as a way to increase housing density in urban areas, and many cities and states have begun to relax regulations to make it easier to build ADUs.