Introduction.- Stochastic Modelling in Life Sciences.- Stochastic Differential Equations and Diffusions in a Nutshell.- Approximation of Markov Jump Processes by Diffusions.- Diffusion Models in Life Sciences.- Parametric Inference for Discretely-observed Diffusions.- Bayesian Inference for Diffusions with Low-frequency Observations.- Application I: Spread of Influenza.- Application II: Analysis of Molecular Binding.- Conclusion and Outlook.- Benchmark Models.- Miscellaneous.- Supplementary Material for Application I.- Supplementary Material for Application II.- Notation.- References.