This chapter discusses some effects of constant light—apparent stopping of the clock, arrhythmia, and splitting of rhythms. When hamsters are placed in constant light, their period lengthens. Their activity time, alpha, shortens, or is compressed. This makes their freerunning record look like a tornado. Splitting was reversed within one to four days when the hamsters were returned to DD; the activity rhythm re-fused into a single component, usually with a longer period length than for the dissociated rhythms. Fruit fly resetting has been studied in great detail, methodically varying the signal duration of the pulse from 0–120 seconds. When this was done, it was found that there was a singularity. The human body temperature rhythm was observed to freerun with a separate period length from the freerunning activity rhythm. The body temperature rhythm was dissociated from the sleep-wake rhythm. Dissociation produces freeruns with different period lengths; splitting produces two components which have the same period length.