Tissue is missing in the given chain. It should be cell – tissue — organ – organ system. A tissue is a collection of similar types of cells which together forms an organ and these organs together form an organ system. Tissues carry out a function together. Similar type of cells ensemble together to form a tissue which is organized in a such a way that it forms an organ like for example stomach. When two or more organs carry out a function of a body together then they are known as an organ system. It is known as an organ system. for example, the digestive system consists of many organs working together.