I am a young doctor whose principal interest is the mathematical theory of chaos and its applicability to computer science security and biology frameworks. To do so, I watch the topological behavior of discrete dynamical systems, like the so-called chaotic iterations. The goal is to measure the quality of unpredictability of such systems and to quantify it, with mathematical proofs. The final concerns encompass, on the one hand the improvement of the security of schemes in the field of cryptography, data hiding, hash functions, pseudo-random numbers generator and sensor networks, and on the other hand the discovery of unpredictable behaviors in biology.