The [εə] diphthong. This diphthong is always followed by the consonant R, and some sources leave it out altogether, as they see the schwa, the second sound in this diphthong, as not really having its own sound. They hear it more going straight from the eh to the rr. And I agree with that, however, I am putting it in because there are just too many sources that list it as its own separate diphthong. The first sound: eh as in bed, the second sound: uh as in supply, the schwa, and then always there is a third sound, and that is the rr consonant, although, the vowel is considered a diphthong (because it only has two vowel sounds).
In slow motion: eeeeehhhhhhh uuuuuuuuhhhhhhh rrrrrrrrr. So the tongue goes from being quite raised in the eh to being very neutral in the uh. Rr, the difference then is in the lips: rr, uh, rr. And also in the throat: the tongue moves back and up a little bit, uh, uh, and the sound feels more like it comes from there.
用慢动作来念[εə]就是：eeeeehhhhhhh uuuuuuuuhhhhhhh rrrrrrrrr。舌头的位置从发[e]音时较高的地方变化到发[ə]音时较中间的地方。而R音和[ə]的区别则在于唇形（注意看视频中的演示），另外还有喉咙处，发[ə]时舌头要略微向后并向上移动一些。
The baby stared at the stairs, preparing to climb.