What causes economic bubbles and subsequent market crashes?

Economic bubbles happen when people get super excited about something and keep buying it even though it's already really expensive, kind of like when you're at a lemonade stand and everyone is buying lemonade even though the glass is full.

People get excited because they think the price will go up even more. It's like when your friend tells you that the toy you want is going to be super popular next week, so you rush to buy it before it's gone.

But sometimes, people start selling the thing they're excited about because they realize it might not keep getting more expensive. It’s like when you find out your friend was wrong and the toy isn’t going to be popular, so you sell yours to get some money back.

This selling makes prices drop fast, and that's why we get a market crash, it feels like everything is falling apart all at once!