Offer your thoughts or opinion on the input financial query or topic using your financial background.

Getting started in stock with one special field of activity
It depends on what you're talking about. If this is for your retirement accounts, like IRAs, then ABSOLUTELY NOT! In your retirement accounts you should be broadly diversified - not just between stocks, but also other markets like bonds. Target retirement funds and solid conservative or moderate allocation funds are the best 'quick-and-dirty' recommendation for those accounts. Since it's for the long haul, you want to be managing risk, not chasing returns. Returns will happen over the 40 or so years they have to grow.  Now, if you're talking about a taxable stock account, and you've gotten past PF questions like "am I saving enough for retirement", and "have I paid off my debt", then the question becomes a little more murky.  First, yes, you should be diversified. The bulk of how a stock's movement will be in keeping with how its sector moves; so even a really great stock can get creamed if its sector is going down. Diversification between several sectors will help balance that.  However, you will have some advantage in this sector. Knowing which products are good, which products everybody in the industry is excited about, is a huge advantage over other investors. It'll help you pick the ones that go up more when the sector goes up, and down less when the sector goes down. That, over time and investments, really adds up. Just remember that a good company and a good stock investment are not the same thing. A great company can have a sky-high valuation -- and if you buy it at that price, you can sit there and watch your investment sink even as the company is growing and doing great things. Have patience, know which companies are good and which are bad, and wait for the price to come to you.  One final note: it also depends on what spot you are in. If you're a young guy looking looking to invest his first few thousand in the market, then go for it. On the other hand, if you're older, and we're talking about a couple hundred grand you've got saved up, then it's a whole different ball of wax. It that spot, you're back to managing risk, and need to build a solid portfolio, at a measured pace.