On the first day, families thank the crows - the bird-messengers. On the second day, they thank the dogs - including pet dogs and stray dogs in the street, who get a marigold garland around their neck and a special meal. There are days for cows, for friends and brothers, and for celebrating yourself.
The most spectacular day is Lakshmi Puja, when families light hundreds of tiny oil lamps along every windowsill, doorway and balcony. From a hilltop above Kathmandu at night, the whole city glows like the sky has been turned upside down.
Children form little groups called 'Bhailo' and 'Deusi' and walk through their neighbourhood singing traditional songs. The neighbours come out to listen and give them sweets, small coins or fruit. It's a bit like trick-or-treating - but instead of costumes, you sing.
Marigolds are everywhere. Whole streets of stalls sell strings of marigolds, and people drape them across their doorways. The bright orange and yellow flowers are believed to bring good luck. After the festival, dried marigolds blow gently around the lanes for weeks.