Gregg Wallace is in Italy, at an enormous pizza factory where they produce 400,000 frozen pizzas each day. He mixes up a 450 kilo batch of dough for the bases; enough for 180 000 pizzas. He watches as each one is stretched to exactly 26 centimetres in diameter, then pricked with 522 holes, each 4mm deep, before they're topped with tomato and disappear into the wood fired oven. It's 25 metres long and the floor is made of rotating panels of volcanic rock heated to 450 degrees Celsius. Gregg's pizzas emerge fully cooked after just 80 seconds. They're topped with cheese, pepperoni, chillies and onions, then frozen and dispatched on their 1000 mile journey to the freezer compartments of British supermarkets.

Meanwhile Cherry Healey is asking if mozzarella – the traditional choice for pizzas - is also the scientific best bet. She finds that not all cheeses are equal, and that to melt well they must sit in a pH zone between 5 and 5.9. This explains why blue cheese and feta don't work on pizza but mozzarella and gruyere do. In Austria, she transforms 400 kilos of pork into pepperoni. She learns that this preserved sausage is fermented and salted to give it a long shelf life. A production process that takes more than 2 weeks.

Historian Ruth Goodman is investigating the technology that allows frozen foods like pizza to be transported across the globe. 150 years ago we were all 'locavores', eating locally sourced food. But in the 1880s the game-changing invention of freezer ships meant that lamb and beef could be shipped from New Zealand and Australia. Combined with the 1938 arrival of the freezer truck, this created the worldwide cold chain that we rely on today. She also meets the man who popularised pizza in the UK back in 1965 when he opened his first restaurant in London's Soho.

Gregg Wallace is in Germany, at a historic factory which produces 600,000 pencils a day. At materials intake he is astonished that the main material in a pencil is not lead, but graphite. He helps mix this with clay to produce a 250-kilo batch – enough for 200,000 pencils. He also discovers why these pencils are hexagonal - because it stops them rolling off the table. And he performs an unusual quality check by throwing his finished pencils from a 25-metre-high tower. When they are chopped open the leads are still intact.

Meanwhile, Cherry Healey is at Manchester University examining the astonishing properties of graphite. She discovers that this highly conductive form of carbon is also able to withstand temperatures up to 3,000 degrees Celsius. More surprising still, if you strip a single layer of atoms from its surface, you produce an entirely new material known as graphene. Thin and virtually invisible, embedding this in our phone screens could mean that in future we could simply roll them up. She is also investigating the science behind graphology and asking if we can evaluate personality from handwriting style.

Historian Ruth Goodman is on the trail of the very earliest pencils in the Lake District. It is a story which begins in the 15th century with the discovery of a huge deposit of pure graphite in the Borrowdale valley. Carved into sticks and wrapped in string, it made a brilliant writing tool. Ruth is also wondering if, in this modern digital age, the pencil is outdated technology. But she finds documents that show the death of handwriting has been prematurely announced on many occasions, dating right back to the invention of the printing press.