Sleep training

Hey mamas, what is your experience with or opinion of “sleep training” a baby, specifically programs that involve any amount of “crying it out”? I’ve become obsessed with researching different approaches of sleep training, the history of these methods, and how being left to cry affects the infant brain. I am really surprised by what I’ve learned over the last few months and I’m hoping to hear some mom stories to supplement the studies I’ve been reviewing. I genuinely appreciate the diversity of perspectives on here and would love to hear your thoughts!