Just like humans, a mouse's personality and energy levels are heavily influenced by what they eat. The foundation of a healthy diet is a high-quality commercial mouse or rat pellet (aim for a protein content of 16-24%). This should be supplemented with small amounts of fresh, safe fruits and vegetables daily. Think of leafy greens, broccoli, a tiny piece of apple, or a blueberry. Fresh, clean water must be available at all times.