On 26th April 1986, Reactor 4 at the Chernobyl nuclear power plant in Ukraine exploded, releasing vast amounts of radiation. Now, 40 years later, it remains the worst nuclear accident in history.

Using the Chernobyl anniversary as a starting point, this week the Unexpected Elements team find out about the weird life thriving at the site of the nuclear reactor. Next up, we discover how radioactive isotopes can help doctors diagnose cancer.

We then turn our attention to ‘gamma gardens’, which were developed by scientists in the 1950s and 1960s to investigate the impacts of radiation on plants. Professor Helen Anne Curry, from the Georgia Institute of Technology, joins us to reveal more.

All that, plus many more Unexpected Elements.

Presenter: Marnie Chesterton, with Andrada Fiscutean and Dr Emmanuel Samani Producers: Alice Lipscombe-Southwell, with Margaret Sessa Hawkins and Georgia Christie

In 2025, Russian-born scientist Kseniia Petrova picked up some spliced frog embryos from a laboratory in France and brought them back to the USA to aid her research into ageing and cancer. She was detained by the United States Immigration and Customs Enforcement (ICE), charged with smuggling and had her visa revoked.

Now though, a judge has ruled that the scientist’s visa was wrongly cancelled.

Inspired by this story, the Unexpected Elements team find out how embryos and sperm behave in space.

Next, we discover that embryos can regenerate limbs, and new research could help us unlock those skills as adults.

We also reveal the unexpected link between frogs and pregnancy tests, and find out about a devastating fungus that’s wreaking havoc on amphibians.

And don't miss probiotics for coral reefs, dessert stomachs and the weird physics of time.

All that, plus many more Unexpected Elements.

Presenter: Marnie Chesterton, with Katie Silver and Camilla Mota Producers: Alice Lipscombe-Southwell, with Ella Hubber and Georgia Christie

This month, India began the immense undertaking of surveying its population of 1.4 billion people in the world’s largest ever census. Inspired by this huge task, the Unexpected Elements team explores some population science.

First, counting – or miscounting – populations. The global human population may be much larger than previously thought as research shows counts may have missed those living in more remote areas. And we learn about the species stuck in a neverending “species limbo”, where they’ve gone unseen for decades but still can’t officially be declared extinct.

Next, we’re joined by geneticist Dr Ambroise Wonkam, one of the researchers behind the Three Million African Genomes project, who tells us why sequencing more African genomes is the key to unlocking a wealth of vital genetics knowledge.

Also, Mumbai’s out of tune musical road, how we know volcanoes are extinct, and the weight of the internet.

All that, plus many more unexpected elements.

Presenter: Caroline Steel, with Chhavi Sachdev and Candice Bailey. Producers: Lucy Davies, with Ella Hubber, Imy Harper and Georgia Christie.