The most common type of mattress, innerspring mattresses are filled with wire coils that support the sleeper. The number of coils can vary from 300 to 800. Mattresses with more coils are firmer and provide good support for people who sleep on their backs or stomachs. Innerspring mattresses with individually-wrapped coils are better for people who sleep on their sides.
Memory foam mattresses were introduced to the market in the early 1990s. Made of polyurethane, they were developed to fill the need for mattresses that could better support the contours of the human body and respond with improved comfort to movement while sleeping. You can place foam padding over an older mattress for a similar effect.
Also known as organic mattresses, latex mattress are made from sap obtained from rubber trees. Since they are manufactured with natural ingredients, latex mattresses are often called "green mattresses." They are hypoallergenic, and the latex helps repel dust mites. Latex mattresses receive praise for combining elasticity with firmness.