Check out which companies are making headlines after the bell on Monday:

Shares of Illumina plummeted 25 percent in after-hours trade Monday, following the company's announcement that it was cutting guidance for its third quarter. The company said it expects estimated third-quarter revenue of about $607 million, compared to analyst estimates of $628 million. The biotech company said the shortfall was driven by a decline in sales of high throughput sequencing instruments, used to analyze large genomes.