Biotech stocks are at a record high

Biotech stocks are having a massive Thursday.

The iShares Nasdaq Biotechnology ETF rallied more than 3% on Thursday to a new all-time high.

The ETF, which tracks stocks in the industry, has seen two big plunges this year, including a 10% correction in April.

Despite these zigzags, the trend is up, and the industry has rallied with other stocks on the market today to reach a new peak.

Earlier on Thursday, the Nasdaq crossed its previous intraday high set in March 2000.

The biotech ETF is now up more than 50% from mid-July last year, when Federal Reserve chair Janet Yellen said that biotech stock valuations "appear substantially stretched."

Yellen has been joined by several Wall Street analysts, who believe the sector is in a bubble, waiting to burst.

Here's a chart showing the sector's climb since 2010.

h/t StockTwits