I spoke to Professor Chae-Won Hoon in her home in Old Seoul. The room is meticulously clean and scrupulously arranged, items on shelves spaced with rigorous precision. Professor Hoon herself sits on a straight-backed chair. Her assistant and relative, Doctor Sebastian Hoon, sat with us and provided support during the interview. It is clear that she takes the care, attention to detail, and commitment to factfulness that characterised her scientific career into every aspect of her life. This was also reflected in her manner of speaking - measured, carefully considered, and precise.

At Professor Hoon’s request, the following transcript is complete and unedited. Voice, video and VR recordings are available as an online supplement.

PY: Thank you again for agreeing to this interview, Professor Hoon. I really appreciate you taking the time to talk to me.

CWH: It is my pleasure.

PY: I want to start by taking us back to the beginning. Where do you think the work that led to the Eterna treatment started, for you?

CWH: Yes. Where did it start?... Well.

There is a pause of around twelve seconds. Professor Hoon nods and looks smoothly towards Dr Hoon.

SH: You may want to start telling us about your ideas when you were working in Cambridge, Professor.

CWH: Of course. I was working on gerontology at the lab of a late good friend and mentor of mine, Professor Timothy Wytes. At the time, we had a lot of interest in ageing. We worked with mice - what was it that made an old mouse different from a young one? Wear and tear, telomeres, degradation of chaperone proteins - but what in particular? This was very difficult work at the time. One of the limitations was that keeping a mouse alive until it was old was not a thing one was permitted to do - unnecessary ageing was considered a cruelty to the animal. So whilst we compared young mice to old mice, our old mice were… not very old. We took samples at different ages and compared them. And I started to think - given these limitations, how can we get the most information that we need? Every mouse was such an investment - and even at a sample a day over their life - we were allowed a year - seemed slow. It seemed to miss the point. I started to think a lot about how samples and information could be gathered continuously - no gaps, no time points. Such data gathering would require new advances in hardware, and actually using, and understanding, the new data would require new techniques and programmes… but the idea was formulated.

PY: Fascinating, thank you Professor. And where did this take you next?

CWH: I carried on my work on continuous sampling both in Professor Wytes laboratory and later when I had set up my own group. I started a collaboration with Doctor Francis Eldram, who worked in nanotechnology. Between ourselves and some very talented other collaborators, we greatly improved our instruments. We… in models, we managed to produce tools that monitored organisms at a cellular level, and that could grow with them. Other advances eventually let us create these tools. We then started learning a huge amount, very fast.

PY: When did you start to realise the potential for what you had created?

There is a pause of around twenty seconds.

SH: Professor.

CWH: Apologies. Can you repeat the question?

PY: Ah - Yes. Of course. After your work creating cellular monitoring systems, when did you start to realise the potential for what you created?

CWH: I see. [there is a pause of five seconds]. The next place this took us was towards a better understanding of not only ageing, but other disease as well. We learnt a huge amount, very fast. [There is a pause of six seconds]. The step from understanding to application took many years and involved many people. But we realised slowly, by degrees, that our same instruments of cellular - and subcellular - monitoring could be used for intervention as well as observation. We could… I designed experiments in mice showing the potential to stall or reverse a large number of model diseases. But it was… only in those animals that we studied from the single cell stage was this intervention complete. That there was perfect recording of biology, thus perfect prevention, and the capacity for regeneration.This was the crux of the issue - if we were observing a cellular system from the very start, from the single cell stage, we were able to intervene perfectly. To undo degeneration. Any later - even one cellular division later - and our interventions were imperfect.

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PY: …Thank you, Professor. So you realised the potential at that stage. How did these ideas and this technology start to translate to what we use in humans today?

CWH: Ah. That was a difficult process. I created my first immortal mouse around three decades after our first experiments showing the capacity for subcellular intervention. I was in my 60s at the time, but well preserved. The approval for Jeremy - the mouse, as you likely have learnt, or perhaps even visited as a schoolchild - took much of that time. The idea of an experiment where we waited for the animal to die, but felt it would not, was a strange one. It took many years of simply waiting, showing the lack of biological degradation, before people started to believe. Then, some things moved very quickly.

It helped that there was, in some places, in some people, a huge hunger for this. For others there was not. Mostly there was reluctance in cultures in which there was belief in an afterlife, or perhaps a denial of death. They saw this as a closing of options. They have, as you would expect, died off - and I hope that they have found peace in it.

In any case, the rich were first, of course; but the rich were already old. And as I had shown, the degree to which subcellular continuous intervention technology produces longevity - what has been called the Eterna treatment, of course - in the already aged is highly variable and incredibly unpredictable. I, and a few relative peers - though years apart in the sensibilities of the past - have been true, true outliers. Anomalies in a way; a very particular genetic make up combined with certain pre-pubescent exposures, I believe, though by definition we of course have no good data for that period of our lives.

Use in pregnancy escalated incredibly quickly once it began. Again, showing it was safe did take time; but then some places took risks, and growth was exponential. It was a great help that by that time, we had managed to make it cheap; to make it technology which safely reproduced itself. All the years after we created the mouse were largely spent on this, and in a way this accessibility might be considered my greatest success. It allowed immortality to be brought about with equality, at least in the new generation.

PY: You mentioned some of the controversy surrounding the Eterna treatment there, Professor. How did this affect you, and how did you respond to it?

CWH: Well. There was a huge hunger for this in many people. Not in everyone. In some cultures, often those who believed in an afterlife, there was reluctance. But… [She frowns. There is a pause of six seconds].

People referred to me as many things. As a devil. As a saviour of some sort. I received many death threats. But I carry on. Those things passed. I persevered, and I believe I was right to do so.

PY: …Thank you again. Another thing I… very much want to ask. It’s something more personal, about the world now. Because, um, of course, you were born already when you pioneered the first Eterna treatment - but have since remained healthy - you are one of the few people in the world today who has not had the, the full treatment. Who could not have the treatment. What perspective does that give you on what is going on in the world, now?

There is a pause of twenty-three seconds. SH and PY speak simultaneously, before CWH begins, cutting them off.

SH: I think…

PY: I’m…

CWH: Who doesn’t want their children to be immortal, indestructible? What mother wants their child to die? Not to age any more than they would like to? The opposite is to want their child to suffer. To age. To die. That we could not share this thing with our children was bitter, and it is bitter now. You ask me my thoughts on the world today, and I have none. I have Sebastian here to remind me of that. I’m dying already. But I do believe that the decisions made were correct.

SH: Perhaps we will end it there, Professor?

CWH: Yes, yes. Tell me what I have next.