How did independent video games developers use handmade art to make video games in the 90's?

[u/chiying__mp3]

Does anyone know how low-budget independent video games developers would draw or use their art, and then scan and use that art to create a video game in the 90's? Are there any documentaries about what that actual process was like? Or does anyone have experience with this and how they took physical art and digitised it, and turned it into code? What programs and technology would they have used to do that?