The study of randomness in macro physical systems was termed classical chaos, and it was the first major field of chaos research for Professor Jensen. In the beginning of the 80s, while attending a lecture on highly excited atoms, Professor Jensen realized that the behavior these atoms were exhibiting very strongly resembled the randomness associated with chaos. Consequently he started exploring the realm of quantum chaos, a field which was still very controversial. Quantum chaos was studying the existence of irregularities and unpredictability of dynamic systems on a very micro level - atoms, electrons, and photons. In 1982 he published a paper on the possibility of seeing classical chaos in quantum mechanical systems. For the next ten years Professor Jensen worked with experimentalists at Stonybrook on defining and exploring quantum chaos. It was in 1991 that he arrived at Wesleyan as a visiting professor, and returned in 1994 to take a tenured position.

At Wesleyan Professor Jensen's interests have taken him far beyond the study of quantum chaos, on which he has published more than 60 papers. One area on which he concentrated was chaos in biological systems. According to Jensen, the important feature of chaos is that one is studying a natural system or a natural phenomenon, which involves feedback processes. The latter are the result of a nonlinear term in the equations describing the system being studied. For example, when estimating the rate of growth of a biological population in 1970, May noticed that after the rate of growth passed a certain critical point, the system would behave unpredictably. Raising the rate meant raising the degree of nonlinearity, and that affected not only the quantity but also the quality of the outcome. That is to say, it affected not only the final population at equilibrium, but also whether the population would reach equilibrium at all. The sheer complexity of these equations can only be solved with the help of a computer, no other methods learned in university would work.

Another area where dynamical systems with feedback exist is economic systems. Many gold seekers have tried to predict the fluctuation of prices on the stock exchange, but the high levels of inherent instability have rendered the feat impossible. Even if the prices of stocks are completely determined by initial conditions, that is, if the system is mechanistic, the behavior of the market on a given day might still satisfy the mathematical definition of chaos: there would be no faster way to compute the outcome than to watch the market perform. Professor Jensen, too, has dabbled in nonlinearity in economics. Together with a former Wesleyan professor he has published what he terms 'a fun' paperÇ on nonlinear dynamics in coupled economics. The attempt was to try and show how difficult it is to infer whose economy is driving whose.

Back to biology, this time on a more cellular level, Professor Jensen has worked on epilepsy and schizophrenia and has published papers in both. There has been a long-ingrained prejudice in the medical community that physiological disorders would be chaotic, that chaos is bad and order is good. However, electrode encephalograms of patients undergoing epileptic seizures displayed brainwaves that were actually very regular. While at Yale in 1992-94, Jensen used computers to analyze electrode encephalograms and noticed that chaos exists naturally in the brainwaves of healthy patients. During the transition to an epileptic seizure, the functioning brainwaves shift from one level of chaos to an intermediate stage, in which they look random, to the actual seizure, where the brain electrical activity oscillates over a large scale, but in a very regular way. As professor Jensen himself puts it 'chaos is healthy, it's the regularity that is unhealthy'. He was very excited to be actually applying his knowledge of chaotic behavior in something that might help treating patients for severe epilepsy.

The applicability of nonlinear dynamics in different fields is reflected by the nonlinear research group, a renewable group of students working with and doing research for professor Jensen. Their majors range from neurobiology to physics to math-economics. Some of them also act as course assistants in professor Jensen's summer course in computational neuroscience at Woods Hole Marine Biological Laboratory. The course, according to professor Jensen, is a wonderful opportunity to find the latest research in the field, while teaching graduate students how to use computers to understand how the brain works.

The latest addition to Professor Jensen's interests is what he terms computational molecular biology. In using the term he refers to the study of how molecules compute the way in which  biological cells process information, and act as a kind of specialized computer. One implication of it is possible insight into how genes regulate and control each other, and differentiation between regulation of genes in health and disease. Rather than dealing directly with chaos, computational molecular biology is really a problem of how to understand feedback dynamics, where chaos is always a possibility. Just as in the epileptic studies, it might turn out that the possibility of chaos, of a dynamical system having behaviors that are very sensitive to initial conditions, can be very healthy for lots of biological and physiological processes including the regulation of genes. Currently Professor Jensen is actively collaborating with a group of researchers at Harvard University who are pioneers in studying large-scale gene expression. According to him, the most exciting opportunity molecular biology can offer is the chance to monitor and understand the interregulation of genes in our bodies. Maybe there is chaos in it, maybe not, but it certainly involves feedback, meaning nonlinear dynamics and that is what professor Jensen intends to explore in the near future. He predicts that the fields of population biology, neuroscience and molecular biology are still to see their heyday, undoubtedly aided by the advent of powerful computers.

In 1985 Professor Jensen made a similar prediction: James Gleick, author of the world bestseller "Chaos", was interviewing participants at a chaos conference in Atlanta. Over lunch he approached Professor Jensen and asked if the whole 'chaos business' was just a passing fad and worth writing a book about. Professor Jensen answered that he had much more at stake than just a book: he was betting his whole career that it was not just a passing fad.

At the beginning of the twenty-first century the fate of nonlinear dynamics looks more than promising, especially with the help of high-speed computers. Each new problem resolved, each new insight gained, breeds numerous other questions and gives birth to limitless possibilities to be explored. Professor Jensen, who has been with the field practically from its inception, is all the more excited about the future applications of chaos theory. As he himself puts it: "I am always looking for Chaos."