Use Retin-A exactly as your doctor has prescribed it for you. Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended. Do not take by mouth. Retin-A is for use only on the skin.
Definition of wall for English Language Learners : a structure of brick, stone, etc., that surrounds an area or separates one area from another : the structure that forms the side of a room or building
Cell wall. A cell wall is a structural layer surrounding some types of cells, situated outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism.