ELI5: What types of products/assets can cause a financial crash/panic/recession?

I’ve recently watched the film Margin Call and began looking into the concept of financial crashes in general but I’m still confused as to how crashes happen. I know we’ve had crashes due to mortgages, a foreign currency and some sort of Dutch plant in the 1600s I (poorly) recall. But, how did these products turn into financial disaster triggers? Is there a recipe of actions that can turn any product into a trigger? Or are only certain types of goods capable of setting off a panic? via /r/explainlikeimfive https://ift.tt/2I51iqv