[rzzzt]

My mind-reading senses tell me parent might be thinking about the scaffolding approach where you show cells the vague outlines of a lung or heart in the form of an extracellular matrix and then they go "hmm, we are building a heart then".

[AndrewDavis]

If I remember correctly you need both. Program the cells to be X organ cells, and provide a scaffold for them to grow on.