Learning how to survive on an increasingly crowded planet is probably our ultimate challenge. But there is one place, home to over a sixth of the world's population, which is already making a good shot at adapting: welcome to India. This extraordinary observational series casts aside the usual preconceptions about the sub-continent, and lets a few of India's 1.2 billion show how their world really works. With astonishing access into the densest districts of Kolkata and Mumbai, it celebrates the impressive resourcefulness, resilience and absolute pragmatism of those living and working there, and reveals the psyche needed to get ahead in the biggest of crowds. This follows two main characters as they employ all their ingenuity to carve out a home. With more people moving to cities in India than anywhere else on Earth, securing that place you can call home is vital for nurturing your family's future. Kaale has come to Kolkata in search of gold - incredibly, he earns a living by sweeping the streets of the jewellery district for stray gold dust. But to fulfil his business ambitions, he must escape his landlord and rent a room of his own. His plan pushes even his resourcefulness to the limit: dredging for gold in Kolkata's drains. Rajesh and his wife Savita have created their home on a Mumbai beach after their controversial love marriage. They support their kids' future with some impressive improvisation, including running their house as a makeshift beach pub selling cane liquor. But then eviction by the Mumbai council threatens their home for good.

This observational series continues to explore what life is really like in some of the densest neighbourhoods on the planet: the backstreets of India's megacities. A popular tactic for people here, so adept at operating in a crowded world, is turning the stuff others would call waste into an opportunity. Johora started out as a rag-picker, but through building a bottle recycling business on a railway embankment, she has big ambitions for her family of seven kids. When the local gangsters increase their protection payment demands, she boldly takes out a big loan and attempts to push her illegal business to another level. And it's not just small waste. Kanye uses a handheld blowtorch to cut up ships discarded by the rest of the world, helping satisfy India's thirst for steel. His dangerous but relatively well-paid job educates his three daughters and provides his ticket to a brighter future. But his hopes are in jeopardy when he is laid off. Ashik buys up beef fat from the abattoir and proudly renders it down to make tallow. It looks disgusting, even before he is plagued by a maggot infestation. But this thrifty use of waste may well be destined for your soap or cosmetics.

With India destined to become the most populous nation on earth by 2026, you've got to be highly tactical in your search for a better life. It's not just about you and your dreams today - it's about the family over generations to come. Prakash and Mangesh are brothers in their early twenties from an illegal settlement surrounded by the buzz of downtown Mumbai. Prakash is deckhand on a yacht while striving to realise his dream and launch a Bollywood career. But his family are playing the long game, and make it clear his sole purpose is to earn enough to fund in their joint future: his brother Mangesh's course in software engineering. Apparently doomed to be the underdog, an audition does finally come Prakash's way. Swapan, a merchant in a hectic fish market, works so hard for his family's future that his wife knows he is ruining his health. When preparations for the huge Durga Puja festival - celebrating the cycle of life - adds yet more stress, it is clear that he is simply fulfilling his role in this cycle. Sujit, who crafts disposable clay tea cups for slim margins in Kolkata, hardly dares dream of seeing his family and newly born daughter hundreds of miles away in his home village. But not prepared to give up, he conjures a business idea that allows them to come to the city - proving that with enough ingenuity, thinking long term can make dreams come true.