Fractal Structures in Biological Systems -- Mandelbrot’s Fractals and the Geometry of Life: A Tribute to Benoît Mandelbrot on his 80th Birthday -- Gas Diffusion through the Fractal Landscape of the Lung: How Deep Does Oxygen Enter the Alveolar System? -- Is the Lung an Optimal Gas Exchanger? -- 3D Hydrodynamics in the Upper Human Bronchial Tree: Interplay between Geometry and Flow Distributi…