Hi in this video, I'm going to be talking about the history of cell biology. So before there was any kind of study of cell biology, we actually had to discover cells. And this was really limited by the fact that cells cannot be seen with the naked eye. And so instead we have to use instruments or specialized tools in order to be able to even look at them much less study them. And so these tools are called microscopes. I'm sure you're familiar with them through your biology classes, your chemistry classes that you've taken in the past. And so we use microscopes in order to magnify an object and that way we can use them to visualize and study cells. So before microscopes were invented, Humankind had to invent the lens. And so these lenses are the types that were using eyeglasses and are now today using cameras and computers. But lenses were originally invented in the 13th century. And so by the mid 1600s, advances in lens technology had increased enough so that people, especially scientists, could begin making homemade microscopes. So this is an example of what a homemade microscope would have looked like. This is just a drawing in from the 16 Hundreds. And you can see that it's first really simple. So this doesn't necessarily look anything like a microscope that you've seen in the past. But this is what they look like in the 1600s. And so this is the type of microscope that a person we're going to talk about whose name is Robert Hooke um used and he was the first person to propose the idea of sales. And so he didn't seek out to determine whether cells existed. That wasn't really what he was concerned with his question. And the reason that he was really studying this at the time was because he wanted to answer the question why are corks so good at holding air in a bottle? Now, this is a really simple question that actually led to this really incredible idea of cells and cell biology. And so what he did is he took a piece of cork, he cut it off and put it under his homemade microscope which at the time had around 30 X. Magnification, which is really small. I mean we have more than that on some fancy cameras and computers today. So 30 X. Magnification is really tiny. But what he was able to see, you can actually see down here, this is a drawing that hook did. And you can see that he saw these compartments that the cork had in them. And he named them cells based off these cells that monks lived in at the time. So what he was seeing was dead plant tissue. He was seeing cell walls. So he wasn't seeing living cells. But he gave them their name and said, okay, these compartments exist inside of these um inside of these organisms. Because cork was eventually at one point living, although it's dead now. And so what are they? And how how can we study them more. So he was really interested in proposing this idea. So then following this drawing and following his idea of cells uh Anton van Leeuwenhoek was the first to visualize live cells. And this was very crucial to the discovery of cells because now we knew that they were living and could move. And so his homemade microscope actually had the ability to magnify up to 300 X 10 times more than hooks microscope. And that's what allowed him to visualize live cells versus dead ones. And so what he did is he did what anyone would do, who has any type of curiosity or and I'm sure we've all done as kids is we just took whatever we could, whatever was around us and looked at it under his microscope. And so he took pond water, he took blood, he took sperm and he just stuck it under his microscope and said, okay, what's there? And so what he saw were live cells that made up blood that made up some of the organisms in pond water and that made up sperm. And so he was so excited and he wrote letters to the Royal Society which at the time was this big scientific organization that sort of control the scientific knowledge at the time. And he said, look what I've seen, I've seen these live cells, they're kind of amazing. And then he sent Hooke robert Hooke to confirm his observations because they were a little skeptical at the time. And so Hook came and he saw these live cells under a microscope. And he wrote back to the Royal Society saying yes, this is what happened. And so right here, you can see there's just a drawing, um evolution, hoax blood cells of what he saw, what he saw blood. So let's now move on to the next concept.

So from the 1600s, when the cells were first discovered, scientists at the time began studying them and said, Okay, well what are the commonalities between all cells on earth? And eventually in the 1800s, they came up with what is now known as the cell theory. And these are basic, just three tenants that are common between all cells on earth. And so the reason that they were able to do this first place is because of advances in microscope technology. So the invention of the compound microscope, which is going to be much more familiar to you. So here's an example down here. You can see that this looks more similar than what uh to what we use today compared to the original image I showed a little while ago. And the reason compound microscopes allowed us to come up with the cell theory is because they had greater magnification so they could zoom in more and they had greater resolution, which is just a fancy term, that means clarity. Now, with a compound microscope, a few scientists were able to really propose the basics of the cell theory. So the first one is um Matias sh Leiden german isn't that great, but bear with me and he discovered that plants, We're made of cells and were derived from a single cell. And he did this in the 1830s. And so around the same time as scientists that he was really good friends with Theodor Schwann discovered that animals we're made of cells. And so they came together and they said, well if plants are made of cells and animals are made of cells, then all organisms are composed of one or more cells. And that makes it the first tenant of the cell theory. And then deriving from that, they said, okay, well the cell therefore is the structural unit of life. So anything is living, the very basic of what it consists of. It consists of cells, anything smaller than a cell is not living. And so they were like, yeah, we discovered the cell theory. So then Richard virtual added to this after 20 more years of research in the 1850s, that cells can arise only by division from pre existing cells is here. So these make up the three tenants of the cell theory. So with that, let's now move on to our next

So we talked about the history and the discovery of cells. So now um let's talk about cell studies and cell research today. So modern cell biology consists of three main field cytology, biochemistry and genetics. So psychology is the study of self structure, biochemistry is the study of cell structure and function. And then genetics is the study of storage and propagation of genetic material. And you may be familiar with these terms from your bio one on one class, but I just wanted to review them quickly. And so um It wasn't just in the 1800s that we were continually advancing knowledge. Science today is continually advancing. It says advancing and adding to the scientific knowledge base. So um these are some terms that you I know you're familiar with from your undergrad or high school classes that I just want to go over them because their terms that really scientists use today to study cell biology. So the versus a hypothesis and that's a statement that's consistent with most observation and experimental evidence today. Then a theory is a hypothesis that has been critically tested multiple times by multiple investigators. So with this definition doesn't make any sense whatsoever in science to say, oh that that's just a theory because it's not a theory has been tested a lot of times and then a law is a theory that has been thoroughly tested and confirmed over a long period of time. So even though they've kept testing, it kept testing it, they haven't come up with any evidence to suggest that anything should be different with the law. And so these three tenants, hypothesis, theory and law. These are really what scientists have used from the 1600s and even before to now to really continually advance the scientific knowledge base. So let's move on.