Fourier Analysis. Knowing how easy it is to go from time to frequency (fft), how there is an uncertainty principle at play between resolution in time and frequ

Fourier Analysis. Knowing how easy it is to go from time to frequency (fft), how there is an uncertainty principle at play between resolution in time and frequency and interesting use cases such as pulling out periodic patterns from data sets (sensor data is great). It's pretty fun and accessible. Introduces beautiful mathematics and you can easily play with them visually in a Python or Julia notebook etc.