Tissues are made up of groups of cells that all have a similar function and structure.
Different species of plants and animals have different types of cells and thus different types of tissues, organs and systems. In humans and other animals, there are four main types of tissues: connective, muscle, nerve and epithelial. Each of these groups can be further broken down, as there are a number of different tissues within each family. For instance, the human body contains three different types of muscle tissue and two types of nerve tissue. Furthermore, blood, bones and cartilage are all types of connective tissue.