If you are looking for a memory foam mattress, it is likely that you are doing your homework, learning about memory foam, shopping for quality memory foam, and even price shopping. While you are doing that, you may be briefly thinking about the foundation for your memory foam mattress. What used to be called a “box spring” is now a foundation. It is the base that your mattress sits on. Box springs, which actually have springs in them, have been replaced with what is now known as a “foundation.” Foundations are generally made of wood and fabric and give a firm, supportive foundation for the memory foam mattress.