Mice need a spacious metal cage, or a glass or plastic tank. Cages should have a deep plastic base rather than a wire base which could damage feet. The bars of the cage should be close enough together (less than 1cm) to prevent escape. Tanks need a wire mesh lid with small holes for ventilation. Remember that mice have very strong incisor teeth and can chew their way through wood.
For two mice, cages or tanks should be at least 45cm long x 30cm wide x 25cm high. Allow a further 30cm for each additional mouse.
The cage or tank should be placed in a well-ventilated warm room away from draughts and direct sunlight or heat. Keep your mice away from constant noise (e.g. the hum of a fridge freezer) or loud noise (e.g. TVs or music systems).