In the
first paper, he introduced
the notion of light quanta
(now called photons) and
used it to explain the
features of photoelectric
effect In the second paper,
he developed a theory of
Brownian 
motion,
confirmed experimentally a
few years later and provided
a convincing evidence of
the atomic picture of matter The third paper gave birth
to the special theory of
relativity In 1916, he
published the general
theory of relativity