Heat oven to 350 degrees F.
Spray 12-cup muffin pan with nonstick cooking spray.
Fill each cup with spinach, goat cheese, microgreens, and bacon.
Pour egg whites into cups, fill to the top.
Top with salt and pepper.
Bake in preheated oven for 20 to 25 minutes.
Cool on wire rack 5 minutes, then remove from pan. Serve warm. Can be refrigerated up to 4 days; microwave on high 30 seconds to reheat.