There are many aspects that need to be considered before you can implement the transition from Classic to Lightning Experience for your Salesforce organization. For example, some items to consider include training users in Lightning, optimizing Salesforce with Lightning features, deploying any customization or changes that were identified during the impact assessment, and migrating users.
If you are migrating users in a phased approach, you should consider using permission sets to activate Lightning Experience for a specific set of users rather than adding to a profile. This can offer a more flexible way to switch on Lightning Experience.
Now, let's look at the features that are available for migrating from Classic to Lightning Experience.