Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Getting started in stock with one special field of activity
Investing only in one industry may be problematic as it is highly correlated. There are factor outside your (or anyones) knowledge which may affect all the industry: If you are familiar with the industry it may happen that you work in that (ignore rest of paragraph if this is not the case). In such case you are likely to have problems at work (frozen salary, no bonus, position terminated) and you need to liquidate the investments at that point (see many advice regarding ESPP). Depending on your field you may have some inside knowledge so even if you would took a position without it you may need to somehow prove it. On the other hand diversifying the investment might reduce the volatility of investment. Rise in oil will cause problems for air industry but will be a boom for oil industry etc. In this way you smooth the grow of the investments. Investing part of portfolio into specific industry may make more sense. It still possibly worth to avoid it at the beginning investor may have trouble to beat the market (for example according to behavioural economics you are exposed to various biases, or if markets are efficient then prices most likely already take into account any information you may have). (I'm still new to all this so it's mostly based on what I read rather then any personal experience. Also a standard disclaimer that this is not an investment, or any other, advice and I'm not licensed financial advisor in any jurisdiction)