The Channels Are In Between the Things
Modern scientific research is finally "discovering" the interstitium, the fluid-filled spaces that exist between all tissues in the body, and considering recognizing them as an "organ".
There's even reference to acupuncture in this CNN article, "It's also the space where the tip of the needle goes during acupuncture, which Theise said might hold clues to how that complementary medicine approach might impact the body."
This is totally in line with 2000+ year-old statements about the nature of the nodes into which the needles are inserted found in 《黃帝內經靈樞》 Huáng Dì Nèi Jīng Líng Shū, 《The Yellow Emperor's Inner Classic - The Spiritual Pivot》, Chapter 1 - The Nine Needles and Twelve Sources:
"The intersections of the nodes, there are 365 of them. Those who know their essentials can say one word and be done, those who do not know their essentials wander limitlessly. As for these nodes, they are the places through which the spirit-qi moves, enters, and exits. 𝗧𝗵𝗲𝘆 𝗮𝗿𝗲 𝗻𝗼𝘁 𝘁𝗵𝗲 𝘀𝗸𝗶𝗻, 𝗳𝗹𝗲𝘀𝗵, 𝘁𝗲𝗻𝗱𝗼𝗻𝘀, 𝗼𝗿 𝗯𝗼𝗻𝗲𝘀."
Here is a link to the original article published in Nature.