My first exposure to investing was when I was about 10 years old. I had saved every dime that I ever got at birthdays/holidays from relatives, any money from pulling weeds for neighbors, and any change that I found on the ground. I had a penchant for numbers/math/compound interest and I would pour over my monthly bank statements excited about the $1-2 I had received in interest. My dad had watched me calculate by hand how long it would take me to get 1 million dollars and then how much interest I would get per day then.
One evening my dad sat me down and explained to me how money could be used to buy tiny parts of companies and then receive commensurate percentages of their profits through dividends which could be thought of in a similar way to the interest from the bank. My dad presented me with two options, if I was interested: I could buy 10 shares of Pepsi at $36 per share or 20 shares of Wendy's at $18. He might have even given me some Value Line pages for each company to read about the projections, I don't remember the details exactly except that he made me take my time and had me wait until at least the next day to decide.
After, careful consideration the next day I said that I was interested in buying the 20 shares of Wendy's. My dad then called the brokerage firm he used and got the shares for me that day. From then on I was the proud owner of 20 shares of Wendy's acquired at $17 7/8 (they didn't like to use decimals back then lol). Looking back I think my dad must have covered the brokerage fees because they would have been $50 or so. From that day on I have always had at least few stocks in my portfolio. I would check the stock prices every day in the paper for many years. Eventually, I ended up selling the Wendy's stock after many years at $50+ per share to help pay for college.
The most valuable part of this was the experiences. It helped open my mind from an early age that money could be used as a tool and deployed in a variety of ways instead of just paycheck in, bills/expenses out. Also, over time I got to live through and experience the highs and lows of the stock market since I had a skin in the game. There was joy watching the markets hit record high after record high seemingly without end in the late 90s and there was an intense feeling of loss when the internet bubble burst and money that you thought had vanished (I can still remember that bottomless feeling in my gut). I was blessed to have this exposure for many years which galvanized my investing habits before I ever started collecting an adult paycheck. After the 2009 crash even though I had a couple investments drop to $0 I never considered pulling out of investing in stock/index funds. I am forever grateful to my dad for starting me on this track, he saw my affinity for numbers and compound interest and took a chance showing me how investing can work.