Learning Aims: Students record their water intake, or how much fluid they take daily, which beverages they prefer, how much urine they approximately excrete. They will answer the questions in the worksheet. Materials: The worksheet with questions and the table, which can be used for data recording. Suggestions for use: Before monitoring their water intake, the students will study the questions below and formulate their hypotheses. Then they will suggest the procedure, which would be used to prove or disprove the hypotheses. They should propose monitoring and recording of their water intake. In the worksheet the students will find a prepared table to record their water intake, but they can propose their own table. The students should agree upon the duration of monitoring, but it is good to propose 4 days - 2 working days and 2 weekend days. Questions: How much fluid do you take per day? Do you drink regularly during the day? How many times per day do you go to the toilet to urinate? What amount of urine per day do you approximately excrete considering the fact that the feeling of urination occurs with the urinary bladder volume of about 300 ml? Will there be a difference between the volume of water taken and water excreted in urine? If so, what is the cause of this difference? What fluid do you most often drink during one day? Questions in conclusion: What is the difference between your fluid intake and the proper fluid intake? As for you, do you have any recommendations? Possible questions: How many litres of fluid have you drunk since your birth? How many litres of fluid will you drink in total during your life provided you live long enough until at least 70 years? How many swimming pools of 50 m x 15 m x 1.5 m could it be? or What can be calculated from the observed data?