Over a person's lifetime they are likely to be prescribed more than 14,000 pills. Antibiotics, cholesterol lowering tablets, anti-depressants, painkillers, even tablets to extend youth and improve performance in bed. These drugs perform minor miracles day after day, but how much is really known about them? Drug discovery often owes as much to serendipity as to science, and that means much is learnt about how medicines work, or even what they do, when they're taken. By investigating some of the most popular pills people pop, Horizon asks, how much can they be trusted to do what they are supposed to?

Ant colonies are one of the wonders of nature - complex, organised and mysterious. This programme reveals the secret, underground world of the ant colony in a way that's never been seen before. At its heart is a massive, full-scale ant nest, specially designed and built to allow cameras to see its inner workings. The nest is a new home for a million-strong colony of leafcutter ants from Trinidad. For a month, entomologist Dr George McGavin and leafcutter expert Professor Adam Hart capture every aspect of the life of the colony, using time-lapse cameras, microscopes, microphones and radio tracking technology.

Grasslands cover one quarter of all land and support the vast gatherings of wildlife, but to survive here animals must endure the most hostile seasonal changes on the planet. From Asia's bizarre-looking Saiga antelope to the giant anteaters of Brazil, grassland animals have adapted in extraordinary ways to cope with these extremes. In the flooded Okavango, lions take on formidable buffalo in epic battles, on the savannah bee-eaters take advantage of elephants to help catch insects and, on the freezing northern tundra, caribou embark on great migrations shadowed by hungry Arctic wolves.

Explore the breathtaking extremes of our planet in this captivating episode. Journey through the vast Hang Son Doong cave in Vietnam, the largest on Earth. Witness the resilience of life in harsh conditions, marvel at the adaptation strategies of species like the blind cave fish and the enduring Arctic wolf pack. In the Arctic, observe the strategic hunt of wolves preying on musk oxen, a dance as old as the Ice Age. In the French Alps, the struggle for mating among common frogs unfolds, showcasing the urgency and challenges faced by cold-blooded animals. Witness the social dynamics of Barbary macaques in the cedar forests of the Atlas Mountains, where survival hinges on social bonds. The forests of Mexico, home to millions of monarch butterflies that huddle for warmth, illustrates the fragility and beauty of nature.
Discover how fire shapes ecosystems in South Africa's fynbos and Northern Australia, crucial for the survival of species like the golden-shouldered parrot. The documentary poignantly addresses the impact of changing climates and human intervention on wildlife, from the endangered elephants of Amboseli, Kenya, to the secretive snow leopards of the Gobi Desert. This episode offers a profound glimpse into the extraordinary adaptations and challenges faced by wildlife across the globe, reminding us of the delicate balance and beauty of life on Earth.

Journey to secret worlds where lives are wrapped in unexpected of ways. The fifth episode of the series takes viewers into the fascinating world of forests, revealing their hidden complexities and the intricate relationships within. Initially perceived as tranquil, forests are in fact bustling with life and intricate ecological interactions. The episode showcases various species, each with its unique lifestyle and survival strategies. Highlights include the Oriental pied hornbills in Borneo, whose extraordinary nesting rituals and partner dynamics are captivating.
The Amazon rainforest is explored, introducing the peculiar treehoppers and their unique communication methods, vital for survival amidst numerous predators like ants and assassin bugs. The episode also delves into the intelligent and cooperative hunting techniques of dholes in the forests of India. The narrative takes a turn to China, focusing on the visually stunning courtship displays of Temminck's tragopans and golden pheasants. In the temperate rainforests of Western Canada, the rare spirit bear and its unique relationship with its habitat are examined.
The episode concludes with an insightful look at the impact of human activity on forests and their inhabitants, particularly focusing on chimpanzees in Uganda, whose survival is increasingly intertwined with human expansion.

In this captivating final episode of the series we meet some incredible conservation champions on nature's front line, fighting to preserve the future of our beautiful planet. The episode opens with a dramatic rescue operation for the critically endangered black rhino, showcasing the efforts of Dumi Zwane and his team to establish a new breeding colony in a safe haven. The focus then shifts to the Centro Jambatu research center in the Andes, where Jaime Culebras works tirelessly to save the last of certain frog species. The documentary also highlights the efforts of Trang Nguyen, who bravely infiltrates the illegal wildlife trade in West Africa to protect forest elephants from ivory poachers. Meanwhile, in Vienna, Katharina Huchler undertakes a remarkable journey to reintroduce the northern bald ibis to Europe after its extinction 400 years ago. Indigenous leader Alessandra Korap's battle to preserve the Amazon rainforest from exploitation is a key focus, alongside Mohamed Nasheed's fight against climate change to save coral reefs and his country.
This episode addresses the broader issue of habitat destruction, emphasizing its role as a primary driver of extinction. It poignantly demonstrates the interconnectivity of life on Earth and the critical importance of conservation efforts.