A cell is the most basic unit of life, a self sustained "mini-city" on a biological level
A tissue is a mass of specialized cells that group together to serve a specific purpose, for example muscle tissue in your eyes move your eye around so you can see and "look around".
An Organ is a large mass of various specialized tissues that all work together to serve a life function or a sense, for example your eye receives light and sends the information to your brain which uses it to form an image, this is done in microseconds spontaneously to provide you with the sense of sight.
An Organ System is a set of organs that each perform a specific purpose but all work together OR in a series to achieve a major life function, for example your digestive tract, starts in your mouth where you chew and swallow your food, then it goes into your stomach to digest it and break it down into small manageable mush, then it makes it's way through your small intestine where all sorts of enzymes further break it down and nutrients are absorbed, then through your large intestine which absorbs water and finishes up whatever's left to do, and then into your bladder for temporary storage until you can get rid of the waste.
a cell is a fundamental unit of life which provides energy for our daily life . many cells coming together forms a tissue and many tissues coming together forms a organs and organs coming together forms a organ system.
Cell- the most basic building blocks of all living things. Tissue- A bunch of cells working together to perform a certain function. Organ- A bunch of tissue working together to help carry out a vital part of life. For example: The heart pumps blood to the brain and other parts of the body. Organ system- Several organs working together to help carry out life