Accidental discoveries are called Serendipity .

Examples of accidental discoveries

Superglue

Dr. Harry Coover accidentally created superglue while trying to make clear plastic gun sights during World War II. 

Pacemaker

Wilson Greatbatch accidentally invented the pacemaker while trying to build a device to record the heart's rhythm. 

Chocolate chip cookies

Ruth Graves Wakefield accidentally created chocolate chip cookies when she ran out of baker's chocolate and used chopped semi-sweet chocolate instead. 

Warfarin

Canadian veterinarian Frank Schofield discovered warfarin in moldy sweet clover hay that was killing livestock. 

Other accidental discoveries 

Teflon

Nylon

X-rays

Penicillin

Safety glass

Sugar substitutes

The microwave oven

The Post-it

The tea bag

Saccharin

How accidents lead to discoveries

Accidental discoveries can happen when people are curious, persevering, and lucky.