Investors may want to keep an eye on the biotech boom.

For one, the sector is still one of the safest, most recession-proof investments around. Two, an aging population is demanding better treatment in an effort to live longer lives. Three, there’s incredible new innovation in gene therapies, immune-oncology, precision medicine, machine-learning drug discovery, and treatments for unmet medical needs. All of which is attracting millions of investors into the red-hot biotech space.

With that, here are five ways to invest in the biotech story.

SPDR S&P Biotech ETF (XBI)

One of the best ways to diversify at less cost is with a biotech ETF, such as the SPDR S&P Biotech ETF (XBI). With an expense ratio of 0.35%, the ETF offers exposure to the S&P Biotechnology Select Industry Index. Some of its top holdings include Biogen, Veracyte, Moderna, Gilead Sciences, Amgen, and VIr Biotechnology to name a few.

Other top biotech ETFs include the IBB ETF, which holds dozens of stocks, including Amgen, Vertex, Gilead Sciences, Illumina, Regeneron, and Biogen to name a few. The IBB, which has an expense ratio of 0.44%, last trade around $133. Or, look at the Ultra NASDAQ Biotechnology ETF (BIB).