 Now I'm going to describe a simple dilution and give you some examples of simple dilutions. So say we have a solution that is 2 mLs of a 10 particle per mil solution. So we know that we have 2 mLs. It's 10 particles per mL. So we have 20 particles that are starting out in this test tube. So we've got 20 particles in there. If we take 1 mL of this solution and transfer it into a test tube that's got 1 mL of buffer, we're transferring 1 mL. There's 10 particles in 1 mL. So we've put 10 particles in here. And we have a total volume because we added 1 mL of buffer of 2 mLs. So again, here we have 2 mLs with 10 particles per 2 mLs. So we're going to simplify that. We have 5 particles per mL. And so that's a 1 half dilution as compared to the 10 particles per mil, 5 particles per mil. And it's 1 mL out of 2 mLs is another way that you can know that it's a 1 out of 2 dilution. So say we took another mL from this first original solution and put it in this test tube. Again, we're transferring 10 particles. But if we put in 9 mLs of buffer here, then we're going to have 10 particles per 10 mLs or 1 particle per mL. That's a 1 10th dilution. And so another way that you can know what your final concentration is, we know this is a 1 10th dilution. We know our original concentration. So this works with dilutions if you know your original concentration, 10 particles per mil. And multiply that by your dilution factor. You're going to get 1 particle per mil, which is what we said this final concentration is. So when you're trying to find out what the final concentration is, if you know your starting concentration and you know your dilution factor, you should be able to come up with your ending concentration. So if you're given an ending concentration and you're giving a starting concentration, you should also be able to determine what dilution factor you need to use to get to that final concentration. So that is a simple dilution. We've just added 1 mL and 1 mL or 1 mL and 9 mLs. We've just added one stock solution and one diluent one time, so it's a simple dilution.