It's a new study to track the spread of COVID-19.
Tens of thousands of households in England are being asked to take part so that researchers can understand the current rate of infection and how many people have developed antibodies to the coronavirus.
The first part of the study will involve around 20,000 households in England, chosen to be representative of the UK population in age and geography.
People will provide nose and throat swabs and answer questions during a home visit by a healthcare worker.
The test is being validated by scientists at Oxford University and will show whether the person has the virus and they will be asked to take further tests each week for five weeks and then every month for a year.
There are plans to involve around 300,000 people in the study over the next 12 months.
Meanwhile, adults from around 1,000 households will also give a blood sample to help determine how many people have developed antibodies to COVID-19. They will be asked to give samples each month for a year.
Blood samples will not be taken from households where someone has COVID-19 symptoms or is self-isolating or being shielded. Swabs will be taken from all participating households, regardless of symptoms.
The volunteers are being selected from people who have already taken part in ONS surveys and have said they are happy to be contacted about further research.
The initial findings of the study, which is run by the Department of Health and the Office for National Statistics, will be released early in May.
The pilot phase will be in England but the study will eventually cover all of the UK.
The study will involve the University of Oxford, data science company IQVIA UK and the National Biosample Centre in Milton Keynes.
Health Secretary Matt Hancock said: "Understanding more about the rate of COVID-19 infection in the general population, and the longer-term prevalence of antibodies, is a vital part of our ongoing response to this virus.
"This survey will help to track the current extent of transmission and infection in the UK, while also answering crucial questions about immunity as we continue to build up our understanding of this new virus.
"Together, these results will help us better understand the spread of the virus to date, predict the future trajectory and inform future action we take, including crucially the development of ground-breaking new tests and treatments."