Active components like transistors, BJTs, MOSFETs, and integrated circuits (ICs) make it possible to control circuits. This video explains the must-have NPN and PNP BJTs. For MOSFETs there are a couple of N-Channels and P-Channels to consider. Basic ICs include some digital logic stuff from the 7400-family as well as the venerable 555-timer to have on-hand. We did not forget Op-Amps either. Spoiler: We do not recommend the ua741!