They may not be household names, but these four companies meet the rigorous investing criteria of these experts. Learn what they are and how they could help you double your money.

A secluded sector of biotechnology -- DNA sequencing and genetic analysis -- is hot once again on Wall Street. Leaders in the sector, like Ilumina, Life Technologies, and Human Genome Sciences, outscored most other biotechs last year.

Despite turbulent times, U.S. markets are rising again. But is this a temporary bump, or the return of a bull market? The sharp-eyed analysts of Morgan Stanley and Goldman Sachs say its the latter, and their money is on strong growth ahead.

Wall Street is littered with so-called hot and smart investors who flamed-out during economic downturns or market crashes. But Marketocracy says its investment management teams are different -- with stock picks that have demonstrated proven, long-term staying prowess.

Mergers and acquisitions are becoming ever more popular, with activity up 24% in the first two months of this year -- after already growing 23% in 2010. Here's how your portfolio can benefit from this trend.

Some investors have been running scared after the quake and tsunami that devastated parts of Japan and left it with an ongoing nuclear crisis. But when there's gloom in the air, there's also opportunity to buy on the dip and gain from the rebound.

As Japan's nuclear crisis deepens, Wall Street may begin to focus on a small group of almost-ignored young biotechs. Known as the bio-defense group, these firms develop products that help protect the population from radiation leaks resulting from nuclear accidents or attacks.

Some stock groups are harder to divine than others, and among those that are tough to figure is the often-opaque insurance industry. But Ray Dirks has been around it for a long time, and when he recommends an insurance stock, it behooves investors to pay attention.

Stem cell research is still too hot for most investors, but NeoStem is starting to change that, thanks to some unexpected events. Among them are the Catholic Church's surprising embrace of NeoStem's research and NeoStem's foothold in China's vast health care market.

Generic drugs are expected to enjoy a banner year in 2011, prompting some investment pros to reformulate their portfolios to get a jump on the transition. For Goldman Sachs, that means betting on several wholesale distributors and retail drugstores that stand to benefit.