| Foreword | |
| INTRODUCTION: Around and Around: | |
| The Importance of Cycles | 1 |
| ONE: Seeing Cycles | 3 |
| Measuring the Tide | |
| A Short Math Lesson | |
| TWO: Putting Cycles on the Map | 9 |
| Found in the Crowd | |
| A Day in the Life | |
| Longer than a Day | |
| THREE: What Drives Cycles? | 15 |
| The Environment's Role | |
| Evidence Against Control by Environment | |
| Internal Sources of Rhythms | |
| FOUR: Discovering the Wheel: The Origin of Cycles | 29 |
| Internal Timekeeping | |
| Tuning Internal and External Rhythms | |
| Constancy Versus Rhythmicity | |
| FIVE: Keeping in Step with Rhythms | 43 |
| Shifting Schedules | |
| Finding the Rhythm Range | |
| Detecting Disease | |
| Treating Disease | |
| Rhythms in Ecology | |
| SIX: Early Adventures in Chronobiology | 57 |
| A Puzzle of Fluctuation | |
| A Puzzle of Timing | |
| A Puzzle of Light | |
| Further Pursuit of Rhythms | |
| SEVEN: Activities in Chronobiology | 65 |
| Running Hot and Cold | |
| Heart Rate | |
| How Time Flies | |
| How Flies Time | |
| Run, Rodent, Run | |
| Tip Twining | |
| Plant "Sleep" Movement | |
| A Colorful Revolution | |
| Bibliography | 83 |