Though springs remain a primary component of many mattresses, foam has emerged as a supportive and comfortable alternative to the innerspring sets that dominated the industry for decades. In order to appreciate the qualities of the best memory foam mattresses, you have to understand the process of production. How they are made creates the distinction between natural, durable, or cheap foam mattresses—important factors to know before any purchase.

Foam mattresses break down into two main categories: memory and latex. Both types are composed of natural rubber infused by different methods with billions of air bubbles, resulting in the airy, almost weightless feeling that has made foam popular in mattress production. The difference between them is the connectivity of the air bubbles. Latex foam, either from natural rubber trees or synthesized by chemicals, is heated and quickly immersed in water to create bubbles that are separate; its air is simply condensed when laid upon. Memory foam bubbles, however, are interconnected, so that all air flows out with pressure, creating the sensation of melting, without the discomfort of the “push back” of the trapped latex air.

Initially developed by NASA as a safety cushion, memory foam requires a more difficult and expensive process in development, but comfort is not its only advantage. Without pressurized air, the memory foam contours to the sleeper’s body and thus provides a stronger, more balanced support. Both categories of foam mattresses will create a softer, more comfortable bed than the traditional spring sets, but for buyers at risk for or already suffering from back pain, the investment in a memory foam mattress pad topper may be a wiser one.