**Preheat the Oven**

Preheat your oven to 375°F (190°C). Grease a muffin tin with cooking spray or line it with silicone muffin cups for easy removal.

**Prepare the Fillings**

If you're using meat, like bacon or sausage, cook it in a skillet until browned and crumbled. Dice your vegetables and prepare any additional fillings you want to add. You can sauté the veggies briefly to soften them, if desired.

**Mix the Eggs**

In a large bowl, whisk together the eggs, milk, salt, and pepper until the mixture is smooth and fully combined.

**Assemble the Egg Cups**

Divide the prepared fillings evenly into the muffin tin cups. Then, pour the egg mixture over the fillings, filling each cup about 3/4 full. Top with a sprinkle of cheese if desired.

**Bake**

Place the muffin tin in the preheated oven and bake for 18-22 minutes, or until the egg cups are set and the tops are slightly golden. You can check by inserting a toothpick — it should come out clean when the egg cups are done.

**Cool and Serve**

Let the egg cups cool for a few minutes in the tin, then use a spatula to remove them from the muffin tin. Serve warm and enjoy!