 Most of us know from experience that our bodies have natural rhythms that affect us in many different ways over the course of a day. We usually wake up in the morning and go to sleep at night, for one obvious example. Some of us will feel sharp in the morning and others will be more alert in the afternoon, but there will be a pattern. These 24-hour rhythms are called circadian rhythms, and we have discovered that they are driven by molecular clocks at work in every cell of our body. It is well known that disturbing these circadian rhythms by shift work as some nurses do, for example, can be bad for your health. It can increase the risk of becoming obese and diabetic, and even becoming depressed. What is much less well known is that our bodies also have natural rhythms that are shorter than 24 hours. Rhythms that may cycle over a few hours. In us, we can see stress hormones go up and down several times a day. Or another example we are not usually aware of is that we cycle through deep and dream sleep several times in any night. We call these fast rhythms ultrading rhythms, and we know almost nothing about them, even though they are always there. The work we do here with Vols is all about understanding how these fast ultrading rhythms are controlled. Are there cellular clocks that control the rhythms in a similar way to the circadian 24-hour clocks? Or are they completely different? To find out, we work with people in our sleep labs, we grow cells, and we study Vols. Why Vols? Well, Vols happen to have very strong ultrading rhythms. Typically, they are awake for an hour and a half, then sleep for an hour, and then wake again. This routine continues day and night. So in many ways, the day is only two and a half hours long. In fact, the ultrading rhythms are so strong that it's almost impossible to detect any circadian rhythms. Vols show very strong ultrading rhythms. But in fact, all animals, including us, show these ultrading rhythms. So, what exactly do we do with these Vols? Well, to begin with, we look at what changes in their bodies during their normal ultradian day. For instance, we took pinpricks of blood from their tails to measure changes in electrical properties of their blood cells over a full ultradian day. We have also surgically placed brain electrodes into some Vols. These electrodes wirelessly transmit information about the activity of the brain, without interfering with the Vols' normal behaviour, such as eating, sleeping and socialising. But to find out what happens inside the cells of the Vols, we sometimes put them down and remove cells and tissues to look at in detail. So far, in our human, Vol and cell experiments, we have discovered that ultrading rhythms operate independently of circadian rhythms. In cells, we know that about 10% of genes have an activity pattern that is circadian. And there are other genes that show an ultradian activity pattern of just a few hours. We can get Vols to shift their feeding times by when we give them food. This changes our ultradian behaviour and is matched with changes in the expression of some genes in the liver. We are still looking for the clock that drives these ultradian rhythms. We have learnt that these rhythms can be seen in the cell's metabolism and we see them in everyday behaviour of the Vol. Whilst this narrows it down, we still are not at a point where we understand these rhythms in full.