import panel as pn
pn.extension()

w1 = pn.widgets.TextInput(name='Text:')
w2 = pn.widgets.FloatSlider(name='Slider')

column = pn.Column('# Column', w1, w2, background='WhiteSmoke')
column

w3 = pn.widgets.Select(options=['A', 'B', 'C'])
column.append(w3)

column

pn.Column(
    pn.Spacer(background='red',   sizing_mode='stretch_both'),
    pn.Spacer(background='green', sizing_mode='stretch_both'),
    pn.Spacer(background='blue',  sizing_mode='stretch_both'),
    height=300, width=200
)

from bokeh.plotting import figure

p1 = figure(height=150, sizing_mode='stretch_width')
p2 = figure(height=150, sizing_mode='stretch_width')

p1.line([1, 2, 3], [1, 2, 3])
p2.circle([1, 2, 3], [1, 2, 3])

pn.Column(p1, p2)

pn.Column(
    pn.Spacer(background='red', width=200, height=200),
    pn.Spacer(background='green', width=200, height=200),
    pn.Spacer(background='blue', width=200, height=200),
    scroll=True, height=420
)