The Next Big Thing: The Wall Street Journal has selected America's top 50 venture capital backed young companies that have the potential to become significant in a diverse range of sectors in coming years.

The Journal says there are some 10,000 privately held, venture-backed companies in the US and to pick the 50 of them with the greatest potential, a team from research firm VentureSource, a unit of Wall Street Journal owner News Corporation, applied a strict set of standards.

To be eligible for the ranking, companies had to have raised an equity round of financing in the past three years and - - because the goal was to identify lesser-known contenders - -they had to be valued at less than $1 billion, which excluded big private companies such as Facebook and Twitter. VentureSource then culled from the remaining 5,194 candidates according to four criteria: the track records of the company's founders and management, and of the investors on its board; the amount of capital raised in the past three years; and the percentage change in the company's valuation in the 12 months ended Nov. 30th. Beyond the numbers, reporters and editors who cover the venture-capital industry for The Wall Street Journal and Dow Jones Newswires also contributed, providing their perspective and expertise.

Pacific Biosciences, of Menlo Park., California, which makes DNA-sequencing instruments, got top ranking.

The company, which was founded in 2004, has developed a disruptive technology platform for the real-time detection of biological events at what it terms single molecule resolution. Single Molecule Real Time (SMRT) Biology promises to revolutionize the life sciences by revealing the underlying molecular interactions and associated networks that define living systems. Pacific Biosciences says unraveling the complexity of biological systems will usher in a greater understanding of the fundamental causes and potential cures for disease, and contribute to progress in other important fields dedicated to improving the health of the planet and its inhabitants.

Pacific Biosciences has raised approximately $266 million to date through a combination of grants and venture capital.

Fusion-io Inc. a Salt Lake City-based maker of flash-memory drives for server got the N. 2 position.

Fusion-io was founded in 2006 by a team of experts with successful track records in the fields of transaction processing, high-performance networking, storage and superclusters, and computing and image processing.

See a complete ranking of the top 50 venture-backed companies- - does not require a subscription.