In a mixing bowl, combine the chopped spinach, artichoke hearts, mayonnaise, sour cream, Parmesan cheese, mozzarella cheese, minced garlic, salt, and black pepper. Mix well until all the ingredients are thoroughly combined.
Transfer the mixture to a baking dish and spread it evenly.
At this point, you can cover the dish with plastic wrap or an airtight lid and refrigerate if you're making it ahead of time. The dip can be refrigerated for up to 2-3 days.
When you're ready to serve, preheat your oven to 350°F (175°C).
Remove the plastic wrap or lid from the baking dish and place it in the preheated oven.
Bake the dip for 20-25 minutes, or until the top is golden brown and the dip is heated through.
Once baked, remove the dip from the oven and let it cool slightly before serving.
Serve the spinach and artichoke dip with your choice of dippers such as tortilla chips, bread slices, or vegetable sticks.