Much has been learned about the subject of noise and random fluctuations over the last 170 years (some old milestones: Brownian motion, 1826; Einstein's diffusion theory, 1905; Johnson–Nyquist thermal noise, 1926), but much remains to be known. This volume will be interesting reading for physicists, engineers, mathematicians, biologists and PhD students. The invited papers in the volume survey classical unsolved problems while the regular papers present new problems and paradoxes.