 So now we have this package.json file, and in it a list of the dependencies that our app has. This is great news. But what happens when those dependencies get out of date? That's an excellent question, and I'm glad that you asked. Let's simulate an app that's gotten minorly out of date by pushing this version back just a little bit. We'll npm install, react, and specify that we want 16.0. Perfect. React 16.0 was installed, and we can check to see that our package.json was updated. It was. It's 16.0 now. Perfect. Let's add another library just for kicks. Let's install react.dom, and we'll also specify version 16.0. We want both of these to be out of date. Again, look at our package.json. See that both of these are version 16. Perfect. npm gives us a command for checking the versions that we have against the latest versions of those packages. It's npm outdated. Run that, and it will give us a pretty handy table. It shows us that both of these packages are indeed outdated. We're using version 16, and we should be running 16.2.0. And now with a flick of a wrist, we can use another command, npm update. We run that, and npm can automatically update these packages for us to the latest version. And let's verify that our package.json was indeed updated, which it was. Now, this was a very happy path. Everything worked very nicely because we were on the same major version. This can be a little bit more involved if you've neglected your maintenance for a while and are switching major versions. Let's do a little work and get this app to have React and React DOM using version 15. We'll install the earliest versions of React and React DOM 15. Now that our package.json has been updated to reflect that, let's run npm outdated again. This is a little bit different because we see that 16.2.0 is the latest, but we're separated by a major version here. So when we run update, we're not going to get 16.2. We're going to get this wanted column. So let's run that npm update. It spins and updates us to 15.6.2. Now that we're updated to the latest on our major, let's run npm outdated again. Instead of this red indicating that we have updates that we can run, we have this yellow. And here it's indicating that we're up to date on our major, but not up to date on the project as a whole. Now, why is this? Well, let's take another look at our package JSON. Before each of these versions is this carrot or hat, it's protecting our app from experiencing any breaking changes by upgrading to major versions too easily. So we can't use npm update in this case. We're restricting it in our package JSON. To get past this hump, we're just going to have to npm install them again and specify the versions that we want. So npm install, I for short, react at latest and react DOM at latest. Now they've been updated to their truly latest version, both in node modules and our package JSON file.