Maybe you could start with a minimal cell, like an amoeba, but what does that look like? How do you know? At what point can a combination of natural and synthetic components be considered a living cell? What parts do you need? How must they interact? Does your cell need to do something specific to be considered fully alive?

Loeb said in 1902 in McClure's magazine: "I wanted to take life in my hands and play with it, I wanted to handle it in my laboratory as I would any other chemical reaction - to start it, stop it, vary it, study it under every condition, to direct it at my will!'

The sponge, while a multicellular organism, is considered an aggregate of individual cells. Around 1900, American Henry van Peters Wilson showed that individual sponge cells can separate and reaggregate to make living sponges again. Generations of MBL researchers have asked how this occurs.

These inventions made observing living cells much easier. Researchers realized that cells not only move as a whole, but that organelles inside cells are constantly moving in the cytoplasm.

In order to understand the role of cells in regeneration, for example, Thomas Hunt Morgan experimented with planarians and hydras, cutting them into bits and observing what happened next.