A crib mattress is a specially designed mattress that fits inside a crib, providing a safe and comfortable sleeping surface for infants and toddlers. These mattresses are typically made from materials like foam or innerspring, ensuring they are firm enough to support a baby's developing body while also being lightweight for easy handling. Crib mattresses come in various sizes and thicknesses, but they must meet safety standards set by organizations like the Consumer Product Safety Commission (CPSC). It's important for parents to choose a mattress that fits snugly in the crib to prevent gaps where a baby could become trapped.