Cells are towns. Tissues are nations. Bodies are planets.
Single cell is a tiny droplets of water surrounded by thin layer of membrane. There are 250 to 300 different types of cells in our bodies, however, all the cells share single genetic information coded by DNA. DNA is like a books of recipes describing how to make various body parts. Each cell combines many recipes to become various types of cells like dental pulp cells or iPS cells.
It is like people go to the library to design their town. Therefore, each town can have different function. Cells (towns) are united to make a tissue (nations); and many tissues are coodinated to generate a body (a peaceful planet).