The bright powder is called 'gulal'. It is made from cornflour mixed with safe colours - reds, pinks, yellows, greens, oranges and blues. People also fill water guns and squeezy bottles with coloured water to spray each other. By the end of the morning, everyone looks like a walking rainbow.
Holi is also a celebration of spring. After the chilly months, the days warm up, the fields turn green and flowers come back into bloom. Throwing colours is a way of welcoming all that brightness into the new season. The streets, the people and the air itself fill with colour.
Holi is famously friendly. Old grudges are forgiven, neighbours hug each other (even if they normally don't get on), and grown-ups join in just as wildly as the children. Everyone wears old white clothes that don't matter - so the colours show up beautifully. Hair, faces and clothes turn into a wild patchwork.
Special foods are part of the day too. Families share sweets like gujiya (little pastry parcels with a sweet filling), and a cold milky drink called thandai. After all the colour throwing, people wash off, change into clean clothes, and visit friends to share food.