  The question whether quantum mechanics is complete and the nature of the
transition between quantum mechanics and classical mechanics have intrigued
physicists for decades. There have been many experimental breakthroughs in
creating larger and larger quantum superposition and entangled states since
Erwin Schr\"odinger proposed his famous thought experiment of putting a cat in
a superposition of both alive and dead states in 1935. Remarkably, recent
developments in quantum optomechanics and electromechanics may lead to the
realization of quantum superposition of living microbes soon. Recent evidence
also suggests that quantum coherence may play an important role in several
biological processes. In this review, we first give a brief introduction to
basic concepts in quantum mechanics and the Schr\"odinger's cat thought
experiment. We then review developments in creating quantum superposition and
entangled states and the realization of quantum teleportation. Non-trivial
quantum effects in photosynthetic light harvesting and avian magnetoreception
are also discussed. At last, we review recent proposals to realize quantum
superposition, entanglement and state teleportation of microorganisms, such as
viruses and bacteria.
