Nesse Distribution was a business I founded based on a system for analyzing Amazon sales data and finding businesses opportunities. In the beginning I would compare Amazon prices with what local stores were charging and find arbitrage opportunities. For example, I once bought soy sauce for $4/bottle at an Asian market and resold them for $24/bottle.
Later I started looking for demand (i.e. keyword searches) with little or no supply (or low quality supply). This led to a variety of interesting micro-businesses, like designing a line of political bumper stickers for the 2016 election, and developing supplies for Wiccans (who, it turns out, are an underserved market).
Nesse Distribution eventually carried over 700 products.