Serendipity denotes the property of making fortunate discoveries while looking for something unrelated, or the occurrence of such a discovery during such a search.

Examples in science and technology:

The German chemist Friedrich August Kekulé von Stradonitz having a reverie of Ourobouros, a snake forming a circle, leading to his solution of the closed chemical structure of cyclic compounds, such as benzene.

Lysergic Acid Diethylamide (or LSD) by Albert Hofmann, who found this potent hallucinogen while trying to find medically useful derivatives in ergot, a fungus growing on wheat.

Rayon, the first synthetic silk, was discovered by French chemist Hilaire de Chardonnet, an assistant to Louis Pasteur. He spilled a bottle of collodion and found later that he could draw thin strands from the evaporated viscous liquid.

The possibility of synthesizing indigo, a natural dye extracted from a plant with the same name, was discovered by a chemist named Sapper who was heating coal tar when he accidentally broke a thermometer whose mercury content acted as a catalyst to produce phthalic anhydride, which could readily be converted into indigo.

Another sweetener, cyclamate, was discovered by graduate student Michael Sveda, when he smoked a cigarette accidentally contaminated with a compound he had recently synthesized.

Penicillin by Alexander Fleming. He failed to disinfect cultures of bacteria when leaving for his vacations, only to find them contaminated with Penicillium molds, which killed the bacteria. However, he had previously done extensive research into antibacterial substances.

Bioelectricity, by Luigi Galvani. He was dissecting a frog at a table where he had been conducting experiments with static electricity. His assistant touched an exposed sciatic nerve of the frog with a metal scalpel which had picked up a charge, provoking a muscle contraction.

X rays, by Wilhelm Roentgen. Interested in investigating cathodic ray tubes, he noted that some fluorescent papers in his lab were illuminated at a distance although his apparatus had an opaque cover

The Slinky was invented by US Navy engineer Richard T. James after he accidentally knocked a torsion spring off his work table and observed its unique motion.