Revelations: `It is in the truth of the minutiae that you begin to build the possibly large'

I was in a fog until I was about 13, unhappy and miserable at school. I didn't know who I was or what I should do. My father gave me a microscope and it became clear.

From the moment my father bought me my own microscope, I spent hours peering down this brass corridor at a brilliantly illuminated stage where I saw translucent micro-organisms ferrying themselves across my microscopic disk. I was fascinated by the relationships of living creatures to one another, and what determined their behaviour. It was like gradually wiping a misty window and discovering an extremely interesting world out there, with as yet ill-understood relationships which, through studying, I could understand.

With my background in amateur zoology and as a collector of pond life, it seemed inevitable that I should go on to the biology side at school. I fell into the hands of the most extraordinary biology teacher, who simply didn't recognise either the timetable or the curriculum. So on weekends we were taken on field trips to classify plants or dredge ponds and net creatures to be taken back for dissection. In the winter we would be taken to the Natural History Museum, in the days before it became a fun park.

In mahogany case after mahogany case were meticulously dissected limbs of various vertebrates, so we became absolutely familiar with the inventory of nature. Gradually I saw that one way to study this world was by looking at the most complicated of all creatures - human beings - and that the best way to study them was to be involved in treating them. The only moment in my life when I decided to do something was when I chose to become a doctor.

Although there was a sharp break when I gave up medicine for the theatre, at some very deep level I never thought I was doing anything different from when I first dredged ponds and looked at the results down my microscope. The interaction of fully conscious beings in opera, and how they signal their desires and wishes to one another, was simply a much more complicated version of what I had seen through that darkened tube.

The best form of theatre direction, just like the best science, starts with small observations. How does that work? Get that straight and your lab is left with unfinished business for the next day, which then leads to further unsolved problems. That's why I've been against large-scale concepts in the theatre.

If there is any rule that I have followed - and I never followed it specifically - it is the magnificence of the trivial. It is the overlooked and neglected which conceal the truth. When students come to me for an opera master-class they expect to be given the big picture, but I do the opposite. For example, at a recent one for Broomhill, we did just a short section of the first act of La Boheme where Rodolfo is making his first tentative flirtation with Mimi. I deal with the microscopic details of embarrassment and shyness, instead of having some great theory about love. What sort of posture does somebody stand in, when they are making a suggestion that they have a faint suspicion will be misinterpreted? So I told my Rodolfo not to look at Mimi, but instead to study his feet, and in that moment they discovered how to play the whole scene. It is in the discovery of the truth of the minutiae that you can begin to build the ingredients of the possibly large. My mother was always a big exponent of this. She was a writer, and she told me never to underestimate the importance of monotony. It is only if things are extremely quiet and monotonous that you can really see what gives the game away.

My life has been a series of these micro-revelations. There have been small moments of understanding when I've seen the world in ways that I had not previously understood.

However, I'm not really interested in my own personal pond life because it seems like maundering. No meditations about myself or my feelings. Instead, I'm deeply committed to the self-evident idea that the nervous system is designed to look outside: we have these extremely elaborate senses which are beautifully designed to furnish us with gigantically detailed information about the world in which we are steering ourselves. It seems a promiscuous mis-spending of funds not to use the gear as it was intended. But it took the microscope to make me truly aware of this truth.

I've still got an old dissecting microscope which is gathering dust. One day when I retire, I would quite like to find a house in the country where I can take flowers apart and look at them through my microscope again.

Yet the area of biology into which I emerged has become so complicated that an amateur with even a complex microscope can't be said to be doing science, and I always want to be on the advancing edges because they are so mind-bendingly interesting.

`Opera Works', a series of six master-classes taken by Jonathan Miller, starts on Monday, 1 September, on BBC2 at 11.15pm.