Here, with great fanfare, is the second installment of Engineer Guy Series #4: the MEMS accelerometer. With typical flair, Bill and his production team take us from the basic concept of an accelerometer (using the familiar ball-on-a-spring model), through the analogous silicon device that lets your smartphone tell up from down, all the way to the anisotropic etching techniques used to manufacture these complex, tiny machines. It’s wonders all the way down, with Bill, as usual. [Thanks, Bill!]