Scientists are coming to believe that your genes may determine whether you're a lark or a night-owl by nature.
And that can have a profound effect on how you cope with things like shift-work.
Breakfast's Sangita Myska was live from the Science Museum in London on how you can take part in a new mass experiment, to find out whether you're an owl or a lark.
She took their instant computer test - and it appears she is neither an owl or a lark!
If you can't get to the Science Museum to take the full test, we have a mini-version which will give you a rough idea of which category you fit in to.
It's part of the Horne-Ostberg test, and it was devised by Professor Jim Horne of the University of Loughborough.
Are you an owl or a lark? Take our test:
1) Breakfast: how's your appetite in the first half hour after you wake up in the morning?
a) Very poor [ 1 ]
b) Fairly poor [ 2 ]
c) Fairly good [ 3 ]
d) Very good [ 4 ]
2) For the first half hour after you wake up in the morning, how do you feel?
a) Very tired [ 1 ]
b) Fairly tired [ 2 ]
c) Fairly refreshed [ 3 ]
d) Very refreshed [ 4 ]
3) When you have no commitments the next day, at what time do you go to bed compared to your usual bedtime?
a) Seldom or never later [ 4 ]
b) Less than one hour later [ 3 ]
c) 1-2 hours later [ 2 ]
d) More than 2 hours later [ 1 ]
4) You are starting a new fitness regime. A friend suggests joining his fitness class between 7am and 8am. How do you think you'd perform?
a) Would be on good form [ 4 ]
b) Would be on reasonable form [ 3 ]
c) Would find it difficult [ 2 ]
d) Would find it very difficult [ 1 ]
5) At what time in the evening do you feel tired and in need of sleep?
a) 8pm - 9pm [ 5 ]
b) 9pm - 10.15pm [ 4 ]
c) 10.15pm - 12.45am [ 3 ]
d) 12.45am - 2am [ 2 ]
e) 2am - 3am [ 1]
6) If you went to bed at 11pm, how tired would you be?
a) Not at all tired [ 0 ]
b) A little tired [ 2 ]
c) Fairly tired [ 3 ]
d) Very tired [ 5 ]
7) One night you have to remain awake between 4am and 6am. You have no commitments the next day. Which suits you best:
a) Not to go to bed until 6am [ 1 ]
b) Nap before 4am and sleep after 6am [ 2 ]
c) Sleep before 4am and nap after 6am [ 3 ]
d) Sleep before 4 am and remain awake after 6am [ 4 ]
8) Suppose that you can choose your own work hours, but had to work five hours in the day. When would you like to START your working day?
a) Midnight to 5am 
b) 3am to 8am 
c) 8 am - 10am 
d) 10am - 2pm 
e) 2pm - 4pm 
f) 4pm - midnight 
At what time of day do you feel your best?
a) Midnight - 5am [ 1]
b) 5am -9am [ 5 ]
c) 9am -11am [ 4 ]
d) 11am -17 
e) 5pm-10pm 
f) 10pm - midnight 
10) Do you think of yourself as a morning or evening person?
a) Morning type [ 6 ]
b) More morning than evening [ 4 ]
c) More evening than morning [ 2 ]
d) Evening type [ 0 ]
Add up the points you scored for each answer (they're in the square brackets).
The maximum score for these questions is 46. The minimum is eight.
The higher your score, the more of a morning person you are.
The lower the score, the more you're a night owl.
How you can find out more
If you want to help the University of Surrey with its research, you can visit its special project at the Science Museum in London.
You can take the full version of their questionnaire - and follow it up if you want with an assessment of your genes.