SCIENTIFIC STUDIES HAVE SHOWN THAT REM SLEEP DEPRIVATION IN ANIMALS LEADS TO THEIR DEATH WITHIN A MONTH, WITHOUT BEING ABLE TO EXPLAIN THIS PHENOMENON. REM SLEEP CORRESPONDS TO ABOUT 25% OF TOTAL SLEEP TIME. IN THE MORNING, THE PRODUCTION OF HORMONES STOPS AND THE BODY IS STIMULATED TO WAKE UP. AT THE SAME TIME, SLEEP ALLOWS THE MUSCLES AND TISSUES OF THE BODY TO REPAIR THEMSELVES AND THE BODY TO REPLACE OLD OR DEAD CELLS. SINCE ENERGY EXPENDITURE IS REDUCED AT THIS TIME, THE BODY STORES ENERGY THROUGHOUT THE NIGHT. IF PEOPLE FAIL TO SLEEP FOR THREE NIGHTS IN A ROW, THEY WILL START TO HALLUCINATE AND HAVE DIFFICULTY THINKING LOGICALLY. THE NIGHT IS A TIME FOR REST FOR BOTH HUMAN BEINGS AND OTHER LIVING BEINGS. IN PLANTS, FOR EXAMPLE, LEAF TRANSPIRATION AND PHOTOSYNTHESIS BEGIN TO INCREASE AT SUNRISE.