Big bangs, vile pongs and Doctor Who: It can only be the Cambridge Science Festival 2011.
Leading Cambridge University experts have opened their labs and lecture halls to the public to reveal the wonder and variety of their subject.
The sixth Doctor Who, Colin Baker, will attend a special exhibition inspired by the BBC programme on Saturday.
It is the country's biggest free science festival and runs until Saturday 27 March.
Last year 35,000 people took part.
This year even babies can get involved.
The director of the Infant Cognition Lab, Dr Claudia Uller, is running a workshop for babies aged up to 18 months old, to help us understand how they make sense of the world around them.
The big popular family-oriented open days are on 19 and 26 March when students and professors engage with young and old.
There are dozens of drop-in events organised, ranging from the science of sweetness to a rocket car derby.
Dave Ansell from BBC Radio Cambridgeshire's The Naked Scientists will show off a selection of his favourite and explosive experiments in a show new to the Science Festival this year.
Comic-book characters will be put under the microscope by Jonathan Wood and Brian Macken, while Dr Lewis Darnell hunts for alien life on other planets.
On 19 and 20 March fans of the fictional spaceman Doctor Who can catch up with K9 and dodge a Dalek at a display organised by the Hyde Fundraisers.
This is a voluntary organisation which raises funds for national charities. This year BBC Children in Need is one of those benefiting from visitors' donations.
But the festival is about so much more than the open days. There are huge numbers of lectures planned as well.
Experts invite you to unravel genome secrets, discover why only some people get fat, and find out about the impact of music on the brain.
For the details of all the events, and what's happening where, go to the University of Cambridge Science Festival website.