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Leading scientists have warned that society has become "supremely arrogant". As a result ignoring the importance of sleep and the body clock has become rampant. Find below the profound impact of internal clocks have on our body. Explore the eight body clock phases and take the quiz to see if you are a morning-type "lark" - or an evening "owl". 1. 06:00-08:59 Heart attack danger zone - Good time to wake up - Heart attacks more likely - Men have their testosterone peak Be careful - this is the time of day your heart is most vulnerable. Blood vessels are stiffer and more rigid, the blood is thicker and stickier and your blood pressure is at its peak. It all adds up to the greatest risk of a heart attack you'll face today. Your body is kicking into gear as sleep hormone melatonin production stops. It is a poor time to exercise. 2. 09:00-11:59 Mind most alert - Maximum cortisol levels - Maximum alertness - Best short-term memory You're probably in work and it's time to get some of the heavy thinking done. The stress hormone cortisol reaches its natural peak giving our brains a boost of alertness. We tend to be most productive before lunch and tests show short-term memory is at its best. Stay busy, there's a big dip coming up. 3. 12:00-14:59 Biological siesta - Increased gastric activity - Post lunchtime dip in alertness - Surge in road deaths With a lunchtime belly full of food, there's a boost in gastric activity. But this soon adds to the 'biological siesta' as alertness dips and affects driving ability. There's a noticeable rise in the number of deaths on the roads from 14:00, particularly in older people. It's also a bad time to drink alcohol as it can make you more drowsy than at other times of the day. 4. 15:00-17:59 Go exercise! - Best lung & cardiovascular performance - Core body temperature rising to its peak - Good time to exercise Go get a sweat on! Body temperature increases in the late afternoon like a natural warm-up, the heart and lungs work better and muscles are 6% stronger than at their lowest point in the day. Some people have even tried using this 'athletic sweetspot' to increase their chances of breaking sporting world records. 5. 18:00-20:59 Watch what you eat - Poor time to eat a big meal - Liver handles alcohol better - Intuitive thinking is better Ready for dinner and maybe a drink? Well you might not want to leave it too late. Emerging evidence suggests the body changes the way it handles food as it gets closer to night-time. Eating big meals in the evening could increase the risk of obesity and diabetes. The liver is more able to deal with alcohol if you fancy a tipple. 6. 21:00-23:59 Getting ready for sleep - Melatonin production building - Core body temperature dropping - Good time to go to sleep Bedtime is fast approaching and the pineal gland in the brain is churning out the hormone melatonin to help you nod off. Core body temperature is falling and the internal body clock is saying it's time to swap the sofa for the duvet. It'll happen first if you're a morning or 'lark' type person, before hitting the 'owls' a bit later. 7. 00:00-02:59 Body enters shutdown - Sleep hormone melatonin peaking - Minimum levels of attention and vigilance - Brain washes itself and consolidates memories It is well and truly bedtime. Hormonal changes in the body say it is time to be asleep. The brain is washing away the waste toxins built up during a hard day's thinking and the bowels are shut down for the night. If you're still awake be careful, levels of attention are at their lowest, making industrial accidents a risk on night shifts. 8. 03:00-05:59 Body fast asleep - Minimum core body temperature - Severe asthma attacks more common - Most natural births occur It's the heart of the night and your body is still some way off waking up and getting you out of bed. Sleep hormone melatonin levels are still high, but glide down as dawn approaches. Your core body temperature is notably cooler than any other part of the day as energy is diverted elsewhere, such as skin repair.