Evil Mad Scientist Laboratories and Eric Schlaepfer have developed a working, transistor-scale replica of a 555 timer chip, which is one of the most common and beloved ICs around. What that means is that every component, which otherwise would be minuscule and built into a tiny integrated circuit, is instead a regular through-hole component. The logic is performed by 13 NPN and 13 PNP bipolar transistors, which perform exactly like the normal-sized 555. Being big means that you can hook up probes and examine every aspect of the circuit. The cool IC legs are a nice touch! If you’d like to build one of your own, EMSL is selling a kit.