Social media check-in as Boston Marathon begins

Security is heightened today at the Boston Marathon, but spirits appear to be high as nearly 36,000 take on the iconic course.

After a moment of silence to honor those impacted by last year’s tragic bombings, the mobility-impaired participants took off just before 9 a.m. ET.

A little over half an hour later, the elite women hit the course, followed by the elite men at 10.

Here is a look at the scene, through the lens of social media: