In today’s episode, Maddie learns all about strong structures. She goes to a nature reserve to find out how a bird makes its nest using twigs, moss, leaves and dried grass. She also meets a bird expert to learn about cup nests. She uses the nature reserve's special camera to see how a bird makes its nest in a bird box, and also gets to witness the magical moment when the bird lays its eggs - one of the eggs hatches into a chick! Next, Maddie heads to a bike helmet factory, where she uses her special proscope camera to see a material called carbon fibre – the threads weave over and under and make the bike helmet really strong.