Tsar Alexander II issues the emancipation manifesto, freeing more than 20 million serfs across the Russian Empire.
Victor Emmanuel II is proclaimed King of Italy, a decisive step in Italian unification.
The Nguyễn court cedes three eastern provinces of Cochinchina to France.
Charles Darwin sets out the theory of evolution by natural selection.
James Clerk Maxwell publishes "A Dynamical Theory of the Electromagnetic Field", unifying electricity, magnetism and light.
Gregor Mendel publishes his pea-plant hybridisation experiments in Brno; the work is widely recognised only after 1900.
France seizes Vĩnh Long, An Giang and Hà Tiên, completing the colony of French Cochinchina.