توضیحات:

- You have to smile 30 seconds a day.

- At the end of the challenge it will be saved as an achievement.

- So you can control which days you have smiled and which not.

- Smiling and laughing is very good for your health, it rejuvenates you.

- When we smile we use between 12 and 17 muscles.

- Smiling also sends more oxygen to the brain.

It also releases endorphins which are the hormones of happiness.

- The smile diary.