Answer and Explanation:
Cell: Molecules get grouped in alive cellular units that have auto replication capabilities. It is the smallest structural unit capable of functioning by itself. A cell is capable of communicating with other cells, their membranes delimitate them and protect them, constituting a selectively permeable barrier, receives signals from the exterior and responds in different ways to the different signals. There are different cells with different sizes, shapes, and forms.
Tissue: A tissue is the organization and association of the same type of cells. Each tissue performs different functions. These tissues can be epithelial, adipose, nervous, muscular, and etcetera.
Organ: An organ is composed of different tissues that work together in a more complex function. Tissues form structures such as the heart, lung, kidney, brain, and etcetera. Each organ has its function.
Organ systems: When different organs get associated and work together, they become a system. Working together in a stable way organs maintain homeostasis.