It’s an amusing, albeit often highly inconvenient, phenomenon that half of the world’s population has to deal with on a regular basis. So what's the science story behind that morning glory? Let’s find out. Drop your comments or any superstitious meaning behind this occurrence .

Their bladder becomes full is what ah heard.

On average, a healthy man has three to five erections during a full night's sleep, with each erection lasting 25-35 minutes. It's common for men to wake up with an erection, informally called a "morning glory". This is in fact the last in the series of night-time erections. The cause of night-time erections isn't fully understood. However, studies suggest they are closely associated with the phase of sleep known as REM (rapid eye movement) sleep. This is when dreaming is most common. Whatever their cause, most doctors agree that night-time erections are a sign that everything is in working order.

source: www.nhs.uk/Livewell/penis-health/Pages/Five-penis-facts.aspx