People across India have new rights to access information held by the government under a law which has come into force nationwide.
The people of India need to be aware of the sweeping new law
The right-to-information law applies to government agency material as well as private sector material which is held by official bodies.
Nine Indian states already have freedom of information legislation.
It is hoped that stronger nationwide laws will increase transparency in public life and help curb corruption.
The BBC's Jill McGivering in Delhi says there are also concerns that implementing the new law in daily life will not be easy.
She says the new law is being hailed by supporters as much stronger than existing state legislation - in fact as some of the most sweeping in the world.
There are exemptions - for example covering personal privacy and some intelligence agencies.
But all of these can be challenged by an over-arching clause citing public interest.
Although the focus is on the public sector, a lot of information in the private sector, reported to government bodies, can now be accessed by the public as well.
Where less powerful legislation existed before, including in Delhi, supporters say the new law will make a huge difference.
There are cases of the poorest people, who are eligible for subsidised rations through a public distribution system, challenging corrupt local officials to show records documenting the process.
As a result, they are now getting their full entitlement for the first time.
Many see this as a major weapon against corruption and bad governance, our correspondent says.
But the biggest battle may be still to come, she adds - most people in India still do not know about the new law.
Others might be cynical about how much difference it can actually make, especially if local officials are hostile to it.
Supporters are also warning that problems like corruption are best tackled by a group of people working together.
Individuals, especially disadvantaged ones, trying to challenge local officials on their own, are still likely to be at risk.