 Good morning class, today we are going to start first chapter for class 9th students CBC board and the first chapter is the basic chapter that you are studying from class 6 and that is sell the fundamental unit of life. So first of all I will ask you some question, hope so you know the answers because those are the basic question. What is the smallest part of our body? Yes, correct cell and what is the branch of science that deals with the study of cell? The branch of science that deals with the study of cell is known as cytology. Now, how do we know that cell is actually the smallest part of our body? So there was a scientist whose name was Antony Molliewell who discovered the first micro-scope and by the help of that micro-scope only we get to know that yes cell is the smallest part of our body. So what was the name of the scientist? The name of the scientist was Anton Van Leuvenhoek, as we discovered the first micro-scope that is the only reason that he is also known as the father of microbiology. So who is father of microbiology? Anton Van Leuvenhoek is the father of microbiology. This is important, you should learn this. Now we will discuss the story that how the cell discovered. What was the ideas that strike in the mind of the scientist that leads to the discovery of the cell? So the name of the scientist who discovered cell is Robert Hoop. You should learn this, Robert Hoop in the year 1665 discovered cell by the help of a dead cell that is cork slice or cork tissue. Now the question arises in your mind that what is cork? So cork is nothing but it is a non-living part or it is a substance that is present on the bark of the tree. So cork cells are the non-living tissues that is present in the bark of the tree. So when Robert Hoop took the cork slice and he viewed under the microscope, he saw that there are small, small compartments, small, small room that similarly looks like a honey comb structure. So that small, small apartment was named as cell. So cell is basically derived from a Latin word whose meaning is little room. So this much, I think you got it. Now this whole story that how the idea came in his mind, what are the things that he assumed that yes we can do this, let us try this. These all story that is the observation result and the experimental result of Robert Hoop is given in a book that is named as Micrographia. Micrographia is the name of the book in which there is an observation of experiments of Robert Hoop. So Micrographia is basically a book that will tell you details about discovery of the cell. So I think that much is enough for you to know what is cell. So moving towards as the cell was discovered, after the discovery of the cell, so many more discovery came. The second discovery is living part of the cell is known as proto-plasmatic was discovered by Parkinje in 1839. All the things which were discovered in that days, it was only possible because of the microscope because by the help of our naked eyes we can't see the cell and we can't differentiate that this is an oval cell and plant cell. So the discovery of microscope is one of the greatest discovery in case of microbiology that help us to see those things that we can't see with our naked eye. So let me draw the diagram of a simple microscope that was used by Robert Hoop in his own experiment during the discovery of the cell. So the microscope was a simple microscope and this simple microscope contains lens that is by convex lens. I hope that you all know about concave and convex lens. The lens which have cave-like structure from both sides is known as concave but those whose structure is not cave-like, it's simply like this, this is known as concave. So the lens that is used in simple microscope was a simple lens that is by convex lens. In order to know the structure how it was looking, I will make and you can easily see this portion is known as eyepiece. This is known as specimen holder, specimen holder means that that part in the microscope where you will keep those slide where you will keep your specimen means those things which you have to view under microscope that should be kept inside this or kept on the specimen holder. This is eyepiece and here is the lens that is known as objective lens. The light which is striking on the specimen, it will go on the objective lens and there will be formation of image and that image you can see by the help of your eye by the part of the microscope that is known as eyepiece. So what we have in this discussion, what can we conclude? Few things. First is that discovery of the cell was done by Robert who came here in 1665. The discovery of the cell was done by a cork tissue that is non-living that is a substance that is present in the bark of the tree. Number three, the cell is made up of small, small compartment means actually one cell is a kind of a small compartment that is arise from the Latin word means cell is originated from the Latin word whose meaning is little room. The living part of the cell is known as protoplasm. The book in which there is a detailed study of the discovery of the cell is known as micrographia. After this Anton von Rivenhoek is the first scientist who discovered microscope and that microscope was a very simple microscope by the help of that microscope only we started to see the image. But always remember Anton von Rivenhoek first of all observed the living things not cork tissue or dead tissues. So Anton von Rivenhoek because of his this contribution in biology is also known as father of microbiology. And the name of the book in which the whole story, this discovery of the cell that how the idea came, what should we do next, which experiment can we do, what are the things that is needed and what are the observations. These whole story is summarized in a book whose name is micrographia. After that Parkinje scientist he also discovered, he also gave something that protoplasm is the living part of the cell. Then Robert Brown came and he discovered that there is master of the cell who is known as nucleus. So first discovery was the cell and after that slowly slowly so many discovery also started because it gives huge contribution or you can say there was so much scope in biology by the help of microscope to see those things which we can't see with our naked eyes.