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 coils, ensuring they are firm enough to support a baby's developing body while also being lightweight for easy handling. When choosing a crib mattress, it's important to consider factors such as size, firmness, and safety certifications. Many mattresses are designed to be waterproof or have removable covers for easy cleaning. Additionally, some models are dual-sided, offering a firmer side for infants and a softer side for toddlers.