Scientist Nina and her young experimenters discover the amazing ways that things can change and react in the everyday world. Nina investigates why we are told to drink milk, with the help of Bud, her taste neuron. Experimenters Kasey and Lily visit Nina in her science lab and use their senses to explore how milk looks, smells and tastes. Nina tells them that milk contains something called calcium that our body needs. Calcium is hard and silvery when it's on its own but when it is added to other things, it can turn white or even disappear - as Nina demonstrates! Then they all visit some underground caves to see how calcium can make pointy hard things that look like giant's teeth! Nina explains that our own teeth and bones need calcium to make them healthy and strong. Back in the lab, the children do an experiment to prove that water from the ground can have calcium in it. They discover that when plants drink water from the ground, they take in calcium. So lots of the fruit and vegetables we eat have calcium in them. Cows and other animals make milk from the grass they eat, so their milk has calcium in it too.