Cell, as we call it, the basic structural (provides structure to an organism), functional (sum total of all functions in cells of an organism results in overall function of the organism) and biological unit of life. The word itself comes from a Latin word "cella", which means a small room or a chamber, and as it should be known because size of cells are extremely extremely small, just like tiny rooms, so rooms do make up a house right? so do cells, group of cells that are speciallized to perform similar functions together make up Tissue, now tissues if considered to be houses, then an Organ is a colony or a block with many houses, and so on the Organs group up, performing functions in a co-ordinated way controlled by the neural or endocrine (system of body that controls relase of hormones) making up Organ system like the digestive system or the skeletol system. This long vertical grouping where from rooms of cells, we come up to a city like organ system wasn't so easy of course to make up. It took millions and millions of years, evolution played its role, many organisms came and went extinct, but the fact that still remains within each and everyone of us is a cell, which did changed in this course of evolution but the basic structure remained the same and that's what makes us "a living organism".
Knowing this cell wasn't easy at the end, it has been on earth since millions of years, from being a prokaryotic cell (a primitive type of cell found in lower organism) of archebacteria, to the most advanced cell found within us, and maybe some modified cells that would certainly be infront of our eyes in future. But we came to know about this small room in 1665, the person who did it was Rober Hooke, who observed this under his own self-made microscope and what he used as his sample was a peice of cork that showed honeycomb like structure, since then came many scientists, the two lab mates from berline giving cell theory then the same cell theory being modiefied by a german pathologist in 1855 then the helical strucuture where we reached to the center of the cell, and found that a cell works on its genetic information, and that same genetic information designs us, as a human from tip to toe.
Now cell itself is a very vast genre, it connects the dots to 1000s of dimensions within biology and medical science, but it matters to us just because of its importance and a very uncertain behaviour causing deadly diseases like cancer. Knowing a cell, modifying it according to our need and using it in a way that benifits the human race on earth could lead to us ranking up in tier of civillization levels