What we call chance discovery is the discovery of a chance, not by chance. Here, a "chance" is defined as a piece of information, about an event or a situation which gives significant impact on the decision-making of human, agents, and robots. This follows the second meaning of ``chance''- a suitable time or occasion to do something - in the Oxford Advanced Learner’s Dictionary, considering that the situation or event occurred at a certain time is more significant than the time itself, and that a decision to do something precedes the action of doing it. We defined chance discovery as the awareness of a chance, defined above, and the explanation of its significance. This triggered researchers in various domains to challenge exploring methods for chance discovery even if the chance is rare and its significance has been unnoticed. They are going much beyond previous data mining and statistics by introducing various ideas.