Creating Egg Muffin Cups is simple when you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a muffin tin with cooking spray or line it with muffin cups.
2. Whisk Eggs: In a large mixing bowl, whisk together the eggs and milk until well combined. Season with salt and pepper.
3. Prepare Vegetables: Chop the bell peppers, spinach, and onion into small pieces. If using cooked sausage or bacon, ensure it is chopped into bite-sized pieces.
4. Combine Ingredients: Add the diced vegetables and cooked meat (if using) to the egg mixture. Stir until evenly distributed.
5. Add Cheese: Toss in the shredded cheese and mix well.
6. Pour Mixture Into Muffin Tin: Carefully pour the egg mixture into the muffin tin, filling each cup about 2/3 full.
7. Bake: Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the cups are set and lightly golden.
8. Cool and Remove: Once baked, allow the muffin cups to cool for a few minutes before gently removing them from the tin.
9. Store or Serve: Enjoy immediately or store in an airtight container in the refrigerator for up to 5 days.

Making these delightful Egg Muffin Cups is a breeze, and your kitchen will smell amazing while they bake!