The gut microbiota is the community of bacteria, archaea, fungi and viruses that lives in the digestive tract of animals. The colon holds the densest microbial community scientists have studied in humans, with between 300 and 1,000 species, although about 99 per cent of gut bacteria come from roughly 30 or 40 species. These microbes break down food that human enzymes cannot, produce vitamins and short-chain fatty acids, train the immune system and help block harmful pathogens. They also communicate with the brain through the gut-brain axis. Imbalances in this community, called dysbiosis, have been linked to inflammatory bowel disease, some cancers and neurological conditions, and researchers are developing microbiome-based treatments in response. The collective genes of these microbes outnumber those in the human genome many times over.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.