Here are two Shiny widgets

Number of bins:

10 20 35 50

Bandwidth adjustment:

…that build a histogram.

renderPlot({
  hist(faithful$eruptions, probability = TRUE,
       breaks = as.numeric(input$n_breaks),
       xlab = "Duration (minutes)",
       main = "Geyser eruption duration")

  dens <- density(faithful$eruptions, adjust = input$bw_adjust)
  lines(dens, col = "blue")
})