Can not recommend this series of videos from Welch Lab[1] enough on imaginary numbers. Deep dives into the history of how complex numbers were "invented" to enable mathematical representation which weren't possible by existing set of numbers. Also draws parallel to "invention" of negative numbers and zero to overcome the limitations of the then present number system (for eg. how to balance books without negative numbers).

[1] https://youtube.com/playlist?list=PLiaHhY2iBX9g6KIvZ_703G3KJ...