There are many investments which have a small risk but also give you a large profit over time. If you invest bitcoin in the early of 2017, you would have multiplied your balance for more than 10 times cause the price of bitcoin in January 2017 was only $1000. And at the end of 2017, bitcoin highest price was $20000. And investing in bitcoin is always the safest way in the cryptocurrency market. Here is another example: real estate. House always increase the price years by years. In my country, you can double your balance with a house. Investing money in real estate is one of the safest way to increase the amount of money in my country and I believe that other countries also have the same situation