 We're going to talk about dilutions. And here I've drawn two containers that contain some solution. In a dilution, you might take 1 ml of this solution on the left and put it in with 9 ml of water. In this case, water is what's considered our diluent. Diluent is the thing that's going to dilute the other solution. So that gives us 10 ml's total volume of our diluted solution. So how is that described? This is where dilutions can get complicated. That can be described as 1 ml to 10 ml's total. It can be described as 1 ml to 9 ml's if you're looking at parts. So it's one part stock solution and nine parts diluent. It can be described as 1 in 10. Again, tells you that 10 is the total volume. It can be described as a 1 to 10 dilution. It can be described as a 1 to 9 parts dilution. It can be described as a 1 tenth dilution because the starting volume is 1 tenth of the final volume. So 1 ml out of 10 ml's. It can be described as a 10 fold dilution because the final is 10 times the starting volume. Or it can be described as a 10x dilution because it is 10 times diluted. So that's a lot of ways to describe 1 dilution. That's why it's really important any time you're doing a dilution in the lab that you read the instructions you're operating procedure, whatever you've been given, really carefully because it's going to be different if you do a 1 in 9 to a 1 to 9 parts because this is 1 ml plus 8 ml's and this is 1 ml plus 9 ml's. So it's important that you read really carefully how you're making that dilution and that you're aware of the ways that dilutions are described because this is going to have an entirely different concentration than this. And so you don't want to use reagents, use things in the laboratory that are not the right concentration. So it's very important when you're reading to know what you're doing. Oftentimes in the lab, we're going to use the terminology of stock. We'll do 1 ml of stock and 9 parts water or 9 ml's. That's also just if you have a 1 part stock, 9 parts. And again, you can go through 1 of 10, 1 tenth. So these are the ways that might be described. And you just want to be really careful that you're understanding how much diluent you're adding and how much of your stock solution or original solution.