I might also include here a remark concerning Stiegler's interpretation of Heidegger's discussion of technics in Stiegler's Technics and Time (volume 1). Stiegler explains Heidegger's theory of technics in a wonderfully simple way that is absolutely productive to think about. He inserts the discussion of phusis that we find in Heidegger's Introduction to Metaphysics right in the middle of a recounting of Heidegger's argument in "The Question Concerning Technology," and the result is to elaborate much better than Heidegger in that later essay how modern technology "challenges" nature. This is expressed vaguely there, and Stiegler wonderfully clarifies it:
Modern technics inflicts violence upon phusis [that most basic determination of being as growth or bringing-itself-forth]; technics is no longer a modality of disclosure in accordance with the growing of being as phusis. Technics becomes modern when metaphysics expresses and completes itself as the project of calculative reason with a view to mastery and possession of nature, itself no longer understood as phusis.
-Technics and Time, I, General Introduction, 10 (my italics)
It is this "in accordance with" that shows that technology is setting against nature or rather against beings as a whole, the totality of existents. Because technics have transformed in their essence to the point at which they disregard or are no longer open to the possibility of beings to grow or bring themselves forth, to upsurge, technics dominates their possibilities, absents them from their own ability to disclose, or, in short, discloses them for them. This taking over of the bringing forth of being, this vicarious or prosthetic control is what constitutes the challenge. I could comment more on this, and perhaps be clearer, but I think the important thing is to note Stiegler has a great explanation here, that reading the Introduction into the questions concerning technics that Heidegger pursues is crucial.