Online courses are very important tools for improving our Data Science skills. 2 years ago, I followed Machine Learning course of Andrew Ng and I learned a lot from Prof. Ng’s clear teaching style. Although there was a Neural networks chapter in that course, it was Octave programming language based. Now, I have started to follow Deep Learning course of Prof. Ng, which is shorter than the previous one. Actually, it takes only 4 weeks to complete the course. And one of its advantages is that it is Python based, which is the most popular Data Science programming language today. The instructors have prepared Jupyter notebooks that are running on the website of Coursera, which simplifies the programming part without requiring to install packages to the local computer, etc. Now, I completed Week 3, and I strongly to recommend anyone who is interested in Data Science to register for this valuable online course.