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That's BetterHelp, H-E-L-P.com. 2019 is Nature's 150th birthday.

To mark this anniversary, Nature is publishing a series of reviews that take a look at the past, present and future of science.

The review I'm looking at today is about the field of epigenetics.

So to start, I should probably tell you exactly what that is.

Epigenetics is, well, it's actually quite hard to define.

This is something which has been debated for decades, in fact.

Epigenetics is a word that's been used and abused, in my opinion.

This is Giacomoka Valley and Edith Hurd.

They're epigeneticists and the authors of the review paper.

To help us better understand what exactly epigenetics is,

it's worth pausing to consider the history. It starts in the 1940s.

It's 1942, and biologist Conrad Warrington first coins the term epigenetics.

He wants to unite the two fields of development and genetics.

His definition was to try and link genotype to phenotype

and try to understand how through development one builds up a complex organism

...