How do you detect a particle that emits no light - in other words, something invisible? This is the intriguing challenge faced by scientists hunting for 'dark matter'. In our series finale, we talk to Elizabeth Bloomfield from Oxford's Department of Physics about dark matter, how we know it exists, and why her research is taking her deep beneath a mountain in Italy in the quest to find it.

What's the best gift you can give? To the millions of people whose lives have been saved by complete strangers, the answer would be simple: blood. But what exactly happens when blood has been donated, and how do we know it is safe? We chat to Dr Richard Mayne from Oxford's Experimental Medicine Division about genomics, Next-Generation Sequencing, blood screening (...and Star Trek).

Could you be a blood-donating hero? Blood stocks are currently critically low, with the NHS Blood and Transplant (NHSBT) group in urgent need of new donors. Click here, and you'll be on your way to saving lives: https://www.blood.co.uk/news-and-campaigns/campaigns/blood-donor-appeal/

Whether you've been served an advert for it, or just heard about it in the media, it's likely that 'Ozempic' isn't a totally unfamiliar word. Now often associated with weight-loss, Ozempic is actually the brand name for a drug used to treat diabetes. So what exactly is it, how does it work, and is it safe? We chat to diabetes and endocrinology (hormone) expert Dr Annie de Bray to find out.

We've all been there...you're on the train, maybe tired after a long day, and all you can hear is one side of a fellow passenger's not-too-interesting phone conversation. Or worse, their choice of music, made tinny and monotonous by the awkward angle of their phone speaker. It's irritating, sure, but for some people it goes beyond mild annoyance, into the realms of anger and panic. For these people - who suffer from a condition called 'misophonia' - phone noise, or sounds such as chewing or breathing, are a real problem. We chat to Dr Jane Gregory, a researcher at Oxford's Department of Experimental Psychology who has misophonia, to find out more about this little-known condition.

With more than 70% of its surface covered in water, Earth is rightly known as the "blue planet". But where did this water - so essential to life - originate? While some theories suggest that hydrogen was delivered to Earth from space via asteroids, new research indicates that the building blocks for water may have been present on our planet all along. We chat to Tom Barrett from Oxford's Department of Earth Sciences to find out more.

What do you do when the subject of your research lies deep beneath the waves? Send down an underwater robot, of course! We chat to volcanologist Sofia Della Sala about her recent fieldwork expedition to Santorini, where she used a Remotely Operated Vehicle, or ROV, to search for hydrothermal vents in the Aegean Sea. These vents - which are like hot springs on the sea floor - could provide vital insight into the volcanic and tectonic activity in the region.

"I still don't believe it happened..."

What's it like to face the most famous clock on television? We chat to Oxford mathematician Dr Tom Crawford - best known as the creator of the award-winning 'Tom Rocks Maths' outreach programme - about what it was like to step into Rachel Riley's shoes on Countdown.

What's the best tactic for tackling the numbers round? How did he prepare? Did he really only have 30 seconds to find a solution? Tom gives us a glimpse behind-the-scenes of this British institution.

One in two people will be affected by dementia in their lifetime - whether that is as a patient, or somebody caring for a loved one. But what happens after a dementia diagnosis? Is there a clear pathway ahead? We chat to Jasmine Blane, a DPhil researcher at the Oxford Brain Health Clinic, about the work she is doing to help support patients in the midst of a dementia diagnosis, and into the future.