36.5C / envelope

The idea comes from the envelope distributed by the Red Cross in an effort to lead people to donate their blood donor cards.
That is, those who receive the envelopes are to mail their blood donor cards to the Red Cross so that the donated cards can be
used for those who need receive blood transfusions.
The thermometer-shaped window on the envelope shows the body temperature starting to rise as a blood donor card is put in it.
When the blood donor card finally settles in the envelope, the body temperature reaches 36.5℃ leading people to cherish donation.Donation can save an invaluable life of someone.